Updated by ALSO Asia Pacific August 2009, March Identify factors important in choosing a fetal heart rate (FHR) monitoring technique.

Transcription

1 E: Intrapartum Fetal Monitoring Original chapter written by R. Eugene Bailey, M.D. and Kim Hinshaw, MB, BS, MRCOG Updated by ALSO Asia Pacific August 2009, March 2011 Objectives At the end of this chapter, participants will be able to: Review the origin of Continuous Electronic Fetal Monitoring (CEFM) and current evidence concerning its use as a screening test. Identify factors important in choosing a fetal heart rate (FHR) monitoring technique. Perform structured auscultative monitoring and continuous electronic fetal monitoring. Review the underlying fetal physiology and response to hypoxia Utilise the mnemonic DR C BRAVADO to interpret electronic fetal monitoring traces. Develop a plan based on the overall assessment of mother and fetus. Discuss the evidence regarding future trends in fetal monitoring. 1

2 History of CEFM In the 17th century Phillipe LeGaust first described fetal heart beats. Subsequently, Francois Mayor in 1818 heard the fetal heartbeat with the ear on the abdomen. With the invention of the stethoscope Evory Kennedy and others described hearing the fetal heartbeat without difficulty for the first time in Modification of this stethoscope was introduced in 1917 by David Hills with the invention of the head stethoscope. The stethoscope, however, could not detect subtle changes nor provide continuous fetal monitoring. This perceived difficulty was overcome in the late 1960s with the development of CEFM and its use rapidly became a part of routine obstetrics. By 1980, nearly half of all women in labour in hospitals throughout the United States were monitored continuously. The use of CEFM has also increased in Australia and other similar countries. Proponents had hoped that, as a screening tool, CEFM would prevent fetal compromise or demise, decrease the incidence of cerebral palsy, and lower numbers of lawsuits. To date it has failed to live up to these expectations. This evidence and the associated issues will be explored in this chapter. Indications for CEFM Indications for CEFM may include those that relate to maternal medical problems, pregnancy related risk factors and labour complications. Indications for CEFM are indicated in the Table below. 1 2

3 Maternal risk factors Fetal risk factors Labour risk factors Previous caesarean birth Gestation >42 weeks Induced or augmented labour Pre-eclampsia Fetal growth restriction PROM >24 hours Antepartum haemorrhage Prematurity <37 weeks Abnormal FHR pattern Maternal medical disease (eg. hypertension, diabetes, cardiac disease, haemoglobinopathy, severe anaemia, hyperthyroidism, collagen vascular disease, renal disease) Multiple pregnancy Oligohydramnios Polyhydramnios Abnormal doppler artery studies Breech presentation Rh isoimmunisation Prolonged labour Abnormal uterine activity Meconium stained liquor Fetal heart rate baselines <110 or >160bpm Maternal pyrexia Fresh bleeding in labour Indications for the use of CEFM in labour Many women remain at low risk during labour and structured intermittent auscultation may be utilised. Indications for CEFM in low risk women include meconium-stained liquor, baseline fetal bradycardia or tachycardia, maternal pyrexia > 38 0 C or C twice over a 2 hour period, fresh bleeding in labour, oxytocin augmentation, woman s request. 1 It is acknowledged that there are variations of a relatively minor nature between the various guidelines being used in maternity care in Australia and New Zealand. It is important that consideration is given to local governance and

4 guidelines, where they exist, and these are used in a systematic way so as to standardise care within an institution. Effect of CEFM on the woman, support people and clinicians The effect that fetal monitoring has on all individuals present during labour and birth must be considered. Use of CEFM decreases mobility, reduces contact between the woman and her companion/s, and changes the interaction and communication with the clinicians. Women do feel that their movement is restricted with CEFM but their preference regarding monitoring method is less important than the support they receive from staff and companions. 3-5 (Category C) CEFM should never be used as a substitute for continuous one-to-one care during labour and women should be informed that continuous fetal monitoring will restrict their mobility. 1 The most recent systematic review in the Cochrane Library included 12 trials (over 37,000 women); only two were high quality. 6 Compared to intermittent auscultation, continuous cardiotocography showed no significant difference in overall perinatal death rate but was associated with a halving of neonatal seizures although no significant difference was detected in cerebral palsy. There was a significant increase in caesarean sections associated with CEFM. Women were also more likely to have an instrumental vaginal birth (nine trials). Access to fetal blood sampling did not appear to influence the difference in neonatal seizures nor any other prespecified outcome. When risk factors develop in labour, CEFM is generally considered and discussed. 1 Any potential benefit of CEFM should be evaluated in light of risk status of the woman. A joint decision between the pregnant woman and her clinician should then be made regarding use of CEFM vs. structured intermittent auscultation (IA) during labour (Category C).

5 Factors to consider when choosing fetal monitoring technique A policy of structured IA may not be present in all birth suites leaving CEFM as the only option. The Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG) 2, as do the National Institutes of Clinical Excellence in the UK 1 and American College of Obstetricians and Gynecologists, presents IA as an acceptable choice for women with low risk pregnancies (Category C). Selection of monitoring technique depends on the following: Risk factors The decision to choose IA or CEFM begins with assessing the woman and her baby for any risk factors then a decision can be made on the best method to achieve optimal fetal monitoring. Clinician availability and level of comfort One of the critical steps in choosing a method of fetal monitoring is an assessment of the personnel available especially in the case of IA. The comfort level of clinicians who may not be accustomed to IA should be assessed. In-service education, clinical case discussion and support should be used to familiarise clinicians with the technique of intermittent auscultation to enhance their skill and comfort level. Informed consent by the woman A discussion of how the baby will be monitored during labour should occur before the onset of labour so that options can be explored and any questions answered. Advantages and disadvantages of both CEFM and IA can be reviewed at this time and woman s preferences can be determined more effectively. Structured intermittent auscultation The decision to use intermittent auscultation (IA) versus CEFM should be made jointly by the woman and her provider 1 (Category A).

6 Frequency of auscultation To date no studies have been done to assess the optimal frequency for continued IA. RANZCOG recommends the frequency of IA as follows: 2 (Category C) Low risk pregnancy High risk pregnancy Active phase Every 15 to 30 minutes Every 15 minutes Second stage Every five (or after each contraction) Every five minutes (or after each contraction) Successful implementation of IA can be achieved if the guidelines below are followed 7 (Category C): Care is provided by practitioners experienced in the technique of intermittent auscultation and palpation of contractions, who are able to recognise abnormalities. Institutional policy determines the technique and frequency of assessment. Clinical interventions follow when non-reassuring findings are present. One to one midwifery care should be provided when utilising IA in labour 7 as the trials comparing IA and CEFM were performed with midwives in constant attendance during labour. Assess FHR before Assess FHR after Initiation of labour or any enhancing procedure Administration of medications Administration or initiation of Admission of woman Artificial or spontaneous rupture of membranes Vaginal examination Abnormal uterine activity patterns (e.g. increased

7 analgesia/anaesthesia basal tone or tachysystole) Evaluation of analgesia/anesthesia (maintenance, increase, or decrease of dosage) Procedure for performing intermittent auscultation Structured IA of the FHR is achieved using a handheld Doppler unit or Pinard stethoscope. 1 Initially the abdomen is palpated to determine the position of the baby. Intermittent auscultation of the fetal heart after a contraction should occur for at least 1 minute, at least every 15 minutes, and the rate should be recorded as an average. The maternal pulse should be palpated if an FHR abnormality is detected to differentiate the two heart rates. 1 Changing from intermittent auscultation to continuous EFM in low-risk women should be advised for the following reasons: Significant meconium-stained liquor, and this change should also be considered for light meconium-stained liquor (see recommendations in Section 12.1) abnormal FHR detected by intermittent auscultation (less than 110 beats per minute [bpm]; greater than 160 bpm; any decelerations after a contraction) maternal pyrexia (defined as 38.0 C once or 37.5 C on two occasions 2 hours apart) fresh bleeding developing in labour oxytocin use for augmentation the woman s request. 1

8 Continuous Electronic Fetal Monitoring (CEFM) The widespread use of CEFM illustrates the limitation common to technological advances especially when applied to the general population as a screening tool. When the prevalence of disease is low (i.e. poor outcome in a low-risk pregnancy) using CEFM to screen for asphyxia can produce false positive results. Therefore, an abnormal tracing is not a very good predictor of poor outcome (low specificity). For example, the changes most associated with cerebral palsy (eg. late decelerations and reduced variability) cannot be used to predict cerebral palsy as they have a false positive rate of 99.8 percent. 8 A normal FHR pattern is predictive of a good outcome (high sensitivity). In Australia and New Zealand, a normal FHR pattern is defined as a baseline rate of with baseline variability of 5-25bpm, with accelerations and without decelerations. A normal FHR has a low probability of fetal compromise. Features which occur in isolation such as baseline rate of , absence of accelerations, early decelerations and variable decelerations without complicating features are unlikely to be associated with fetal compromise. 2 Over ninety percent of cases of cerebral palsy are determined not to be associated with intrapartum events and most perinatal asphyxia, even if severe, does not result in long-term neurological outcomes. 8 9 Most of the problems encountered with CEFM are related to the lack of conformity in interpretation of fetal monitor traces and generally poor education regarding the overall assessment and response. In common with the rest of the developed world, failure to diagnose or respond appropriately to CEFM abnormalities continues to be a finding in reports into perinatal deaths RANZCOG recommends that health professionals access regular, multidisciplinary education and credentialing on EFM; the education should include relevant maternal and fetal pathophysiology as well as consistent grading/classification systems. 2

9 CEFM and record keeping In order to ensure accurate record-keeping regarding EFM: 1 The date and time clocks on the EFM machine should be correctly set. Traces should be labelled with the woman s name, date and hospital number. Any intrapartum events that may affect the FHR should be noted at the time on the FHR trace, which should be signed and the date and time noted (for example, vaginal examination, FBS or siting of an epidural). Any member of staff who is asked to provide an opinion on a trace should note their findings on both the trace and the woman s clinical records along with the date, time and signature. Following birth, the healthcare professional should sign and note the date, time and mode of birth on the FHR trace. The FHR trace should be stored securely with the woman s clinical records at the end of the monitoring process. Interpretation of CEFM The interpretation of a CEFM trace should take into consideration the stage of labour, progress in labour, maternal and fetal condition, and prior or additional risk factors present as well as the features of the FHR trace and the availability of extra tests or assessments. 1 To start with, it is useful to consider the physiological changes that are occurring during labour. Physiology Over the last three decades of continual use and study, CEFM has proved to be effective at identifying the baby who is normally oxygenated but has low specificity for identifying the hypoxic baby. Appropriate management during labour is largely dependent on accurate interpretation of

10 fetal heart rate patterns. 12 It has been suggested that this flaw has been due to a lack of understanding of the underlying fetal physiology before CEFM was introduced. 13 Knowledge of fetal physiology, specifically the effects of umbilical cord compression and occlusion has been informed by animal studies 14 Physiology of the utero-placental unit The structure and function of the placenta is crucial to adequate gaseous exchange between mother and her unborn baby. Changes to the uterine arteries occur early in the gestation whereby tightly coiled, high pressure vessels become widely dilated vessels to accommodate the increased blood flow. Growth and development of the placenta is characterised by a progressive decrease in vascular resistance (auto regulation); arteries lose their ability to respond to changes in maternal blood pressure. Because of the lack of auto regulation within the uterine arteries supplying the placenta, blood flow can be decreased due to events such as uterine contractions and maternal hypertension or hypotension. Blood flow to the uterus cannot be increased beyond the maximal blood flow to the uterus but it can be facilitated by changing maternal position to decrease vena caval compression or by the use of tocolytics to reduce uterine activity. Gaseous exchange between mother and fetus occurs in the intervillus spaces of the placenta and is totally dependent on adequate blood flow to the uterus. Oxygen and carbon dioxide transfer occurs by diffusion across the membranes separating maternal and fetal blood. Although this is an efficient process, facilitated by the differentials in gaseous pressure between the maternal and fetal circulations, the fetus is relatively PO 2 poor compared with adult arterial values. The umbilical vein, which carries oxygenated blood, holds approximately the same PO 2 (35mm Hg of dissolved oxygen) as the maternal veins. In order to support efficient gaseous exchange the fetus has several

11 physiological mechanisms to support normal metabolism even though the fetal PO 2 values are similar to his/her mother s venous circulation: fetal blood has more haemoglobin than the adult, fetal haemoglobin has a greater oxygen affinity than adult haemoglobin, some organs are over-perfused (sometimes known as fetal brain-sparing ) increased cardiac output and rate results in an increased turnover of circulation, more capillaries per unit of tissue than adults. Under normal circumstances the fetus is well oxygenated and some organs, such as the brain, the adrenals and the kidneys are over-perfused to ensure adequate oxygenation. Physiologic response to hypoxia Normal aerobic metabolism can be maintained during transient decreases in blood supply such as those incurred during labour, as long as the oxygen saturation in the intervillus space remains above 50%. During a significant fall in PO 2, blood flow is redistributed to the vital organs; specifically the heart, the brain and the adrenals. Whilst the blood flow to these organs can be increased by %, there is a consequent decrease in blood flow to the intestinal tract, the spleen and the kidneys and limb movement is curtailed. This brain-sparing response allows the fetus to sustain relatively long periods of limited oxygen supply. The negative effects can be seen in the growth restricted fetus, where there is discordant growth between the abdomen and head, reduced liquor volume and reduced fetal movements. During periods of decreased oxygen supply, oxygen consumption is reduced and metabolic needs are subsidised by anaerobic metabolism. Both aerobic and anaerobic metabolism produce Adenosine triphosphatase (ATP) which is essential for cellular metabolism. Aerobic metabolism occurs in the

12 presence of normal glucose and oxygen levels and produces 38 ATP molecules for every 1 molecule of glucose. The by-products of aerobic metabolism are water and carbon dioxide, both easily excreted via the placenta. 17 Anaerobic metabolism is an inefficient way of producing glycogen for cell metabolism producing just 2 ATP molecules per one molecule of glucose. The by-products of anaerobic metabolism are lactate and hydrogen ions, neither of which is easily excreted via the placenta. The culmination of anaerobic metabolism is an accumulation of these by-products in the fetal blood, raising the serum lactate levels and lowering the blood ph to produce metabolic acidosis. Changes in FHR patterns are mediated via the vagus nerve and chemoreceptors and baroreceptors in the aortic arch and carotid bodies in response to changes in oxygen, carbon dioxide, hydrogen ions, and arterial pressure. Since it is impractical to continuously measure fetal oxygenation and ph which is the most accurate measure of fetal wellbeing, the FHR pattern becomes a screening test that identifies a fetus that would benefit from ph or lactate assessment, a more accurate measure of fetal wellbeing. DR C BRAVADO The mnemonic DR C BRAVADO provides a systematic approach to the interpretation of FHR tracings for both CEFM and IA (Category C). In using this mnemonic for CEFM a fetal heart rate pattern will be defined as a graphical representation of both uterine activity and fetal heart rate or a composite of intermittent auscultations between contractions (baseline), and five second intervals for 60 seconds during and after palpated contractions if using IA. Determine Risk Contractions

13 Baseline RAte Variability Accelerations Decelerations Overall assessment and plan Determine Risk The woman s history and any risk factors should be noted before commencing CEFM. Fetal reserve is indicated by assessing the clinical situation. Is this a term, low-risk fetus or are risks present such as growth restriction or particulate meconium? Is labour progressing well or is there associated dystocia? Is an assisted vaginal birth likely? It is also important to consider if multiple risk factors are present rather than focusing on one isolated risk factor. For example, smoking as an isolated risk factor may not change the approach taken clinically whereas smoking in a teenager with iron deficiency anaemia and an eating disorder may signal a more high-risk situation. The identification of antenatal or intrapartum risk factors should lead the clinician to consider the use of CEFM as the most appropriate method of assessing fetal wellbeing during labour. Contractions The electronic fetal monitor uses a pressure transducer to measure amplitude and frequency of contractions. It is not possible to assess the strength of contractions from an external transducer, however if well placed on the maternal fundus the frequency and regularity of the contractions can be successfully recorded. Assessment of the frequency and regularity of contractions and whether there is evidence of hyperstimulation should be part of the overall assessment of CEFM. It is difficult to recognise FHR decelerations without establishing when a contraction begins and ends. Changes in

14 fetal heart rate patterns may be seen during uterine tachysystole (>5 contractions per 10 minutes for at least 20 minutes) or uterine hypersystole/hypertonus (a contraction lasting at least two minutes). Uterine hyperstimulation syndrome is defined as either uterine tachysystole, hypersystole or hypertonus with fetal heart rate changes such as persistent decelerations, tachycardia or decreased variability. 1 When compared with labours where the contraction pattern is less than 5 in ten minutes, uterine hypertstimulation is associated with significant oxygen desaturation in the fetus and higher rates of neonatal acidaemia at birth. 22 Baseline Rate The baseline rate is determined over a 5-10 minute period, excluding accelerations and decelerations and in the absence of fetal movement or uterine contraction. The baseline is expressed in beats per minute (bpm). A normal baseline is bpm. 2 A change in baseline FHR occurs when the change is present for 10 minutes or more. This definition is fundamental to interpreting changes in FHR patterns. A change in baseline rate can be due to prematurity, change in fetal status, maternal fever, position or medication. A gradually increasing baseline accompanied by decreased variability or decelerations (or both) frequently indicates fetal hypoxia. The parasympathetic nervous system matures more slowly than the sympathetic nervous system and is not fully mature until around 28 weeks gestation. Because of this, the inherent fetal heart rate is increased earlier in the gestation and decreases towards term. 13 Bradycardia Definition : baseline rate of <110 bpm 2

15 Bradycardias can be mild or severe. Consideration should be given to the presence of other features within the FHR pattern. If not associated with other abnormalities, such as decreased variability or decelerations, it does not indicate hypoxia. Mild bradycardia is a rate of 100 to 110 bpm. Even bradycardias <80 bpm are not associated with fetal compromise if variability is retained. This may be attributed to congenital heart disease such as complete heart block, myocardial conduction defects associated with collagen vascular disease in the mother, beta-adrenergic blockers and occasional idiopathic baseline bradycardia. 13 Mild bradycardia is associated with post-dates infants and the occipito-posterior position. Bradycardia which occurs in late second stage is thought to be triggered by vagal stimulation caused by head compression. As long as the fetal heart remains above 80 and variability is retained, a previously non-compromised fetus can usually tolerate this. 13 Compromise of gaseous exchange within the intervillus space occurs in situations where the bradycardia is prolonged or recurrent, regardless of whether the bradycardia is alone or associated with other abnormalities. In these cases metabolic acidosis and fetal hypotension will occur and variability will be reduced or absent. This type of pattern is sometimes known as a terminal FHR pattern. It can often be seen as an evolution of late or complicated variable decelerations and can be associated with uterine rupture, placental abruption, severe fetal growth restriction, feto-maternal haemorrhage and just before fetal death. 13 Tachycardia Definition: baseline rate greater than 160 bpm 2 Fetal movement, maternal anxiety or fever, maternal dehydration or ketosis and beta-adrenergic agents all may cause fetal tachycardia that is unassociated with fetal hypoxia. Fetal immaturity, thyrotoxicosis and anaemia may also cause a mild tachycardia. Variability in these situations will be

16 normal and the tachycardia is usually less than 180 bpm. Persistent tachycardia greater than 180 bpm, especially if maternal fever is present, suggests chorioamnionitis. A fetal heart rate greater than 200 bpm is frequently due to fetal arrhythmia or other congenital abnormality. A transient tachycardia can usually be seen during recovery from an acute hypoxic episode. This response should be considered a normal physiologic response, secondary to catecholamine release. Consideration should always be given to the presence of the other features within the FHR pattern. Fetal compromise is more likely if the tachycardia is associated with reduced or absent variability and decelerations. 44 Variability Definition: variability is the minor fluctuation around the baseline fetal heart rate, assessed by estimating the difference in beats per minute between the highest peak and lowest trough of fluctuation in one minute segments. Normal baseline variability is defined as 5-25 bpm, reduced is 3-5 bpm, absent <3 bpm, increased or salutatory >25 bpm. 2 The fetal heart rate normally exhibits variability with an average change of 10 to 15 bpm of baseline rate and is linked to the fetal central nervous system (CNS) and reflects fetal cerebral activity. The variable fetal heart rate pattern is due to the balancing of parasympathetic and sympathetic stimuli by the cardiorespiratory centre within the brain and influenced by baroreceptor and chemoreceptor response. Variability is therefore a vital clue in determining the overall fetal condition. The most common cause of reduced variability is the fetal sleep state. Normally grown and well nourished babies may have decreased variability with no known cause during sleep cycles. Sleep cycles of 20 to 40 minutes or longer are the most common cause of a normal decrease in FHR variability. Variability is also influenced by maternal medications, especially those which depress the maternal CNS such as opioids, beta blockers and magnesium sulphate. Other causes can be anencephaly (anencephalic

17 babies will have a relatively flat baseline because their cardiorespiratory centre is absent), congenital cardiac or neurological abnormalities. Steroid administration to induce fetal lung maturation also reduces variability in the 24 hours following administration. 3 Consideration should always be given to the other features within the FHR pattern and the duration of the episode. Loss of variability in the company of other abnormal features, such as complicated or late decelerations and a rising baseline, is more indicative of fetal compromise than baseline variability alone. 13 Absent baseline variability is the most specific finding associated with fetal asphyxia but still has a very poor sensitivity, identifying only 17 percent of fetal asphyxia in one small study. In these cases the estimated positive predictive value ranged from 2.6 percent to 18.1 percent and the negative predictive value ranged from 98.3 percent to 99.5 percent. Thus variability, when present, is correlated with a good outcome. Loss of variability is the pattern most indicative of increased risk since it may be the cumulative result of previous non-reassuring factors and may indicate decompensation of the fetal compensatory mechanisms. When accompanied by late or variable decelerations, decreased variability increases the possibility of fetal acidosis and low Apgar scores if it remains uncorrected. Sinusoidal pattern A sinusoidal pattern is described as a regular, smooth, undulating oscillation resembling a sine wave with 2-5 cycles per minute and an amplitude of 5-15 bpm above and below the baseline. Variability and accelerations are absent. This may be a terminal pattern representing a severely impaired infant and requires immediate intervention. It is associated with severe fetal anaemia and hydrops. A false sinusoidal pattern is not uncommon, particularly if it is intermittent and shows normal variability. In a true sinusoidal pattern variability is absent.

18 Accelerations Definition: transient increases in the fetal heart rate of 15 bpm above the baseline, lasting for 15 seconds or more. 2 Accelerations associated with fetal movement or stimulation are often used as a measure of fetal well-being. Absence of accelerations in established labour does not necessarily indicate fetal compromise but does indicate the need for further evaluation especially if there are other features of the FHR pattern that are of concern. When accelerations (shouldering) are seen in association with contractions and variable decelerations they may indicate partial cord compression. Their disappearance may signal fetal hypoxia especially when associated other indicators of compromise, such as complicated variable decelerations, decreased baseline variability, baseline tachycardia or bradycardia. During active second stage, decelerations due to the vagal stimulation caused by head compression are much more likely than accelerations. If repetitive accelerations are noted at this stage, care must be taken to ensure that the fetal heart rate and not maternal heart rate is being monitored. Other features that may indicate the pattern is maternal heart rate rather than fetal can be a sudden change in the baseline rate and a pattern that now looks very different Decelerations During intermittent auscultation it can be difficult to classify decelerations when they are heard. Distinguishing the end of the deceleration, the rate of rise to baseline, and its relationship to the palpable contraction should help in identifying a worrisome pattern. At any time during fetal monitoring changing to CEFM should be considered if further elucidation of decelerations is warranted. Decelerations are classified as early, variable, prolonged or late depending upon their

19 relationship to the contraction, to each other and upon the presence of other features within the FHR pattern. Early decelerations Early decelerations are transient decreases in FHR, occurring with, and mirroring, the uterine contraction. They are uniform in shape, begin and end with the contraction and the peak of one coincides with the nadir of the other. They should not usually fall more than 60 beats from the baseline and seldom go below 100 bpm. 2 Early decelerations are the least common deceleration and considered benign if no other abnormalities of FHR are noted. Early decelerations are most commonly seen during fetal sleep as the activity of the parasympathetic nervous system is quieter at this time. As early decelerations are probably due to head compression they are only seen during labour between 4-8cm dilatation. They are less likely to be seen in advanced labour because of the greater vagal stimulation as the head descends through the pelvis. Variable decelerations Variable decelerations are variable in shape and variable in relationship to the contraction. Generally they will have a more rapid, sharp descent and recovery than early or late decelerations. There are two classifications; variable and complicated variables. Variables are defined as a repetitive or intermittent decrease in the fetal heart with rapid onset and recovery. These most commonly occur simultaneously with contractions and are often benign. Characteristics that indicate they are benign include rapid descent and recovery, good baseline variability and accelerations at the onset and at the end of the contraction (the classic or M shape) often described as shoulders. Complicated variables Complicated variables are associated with other abnormal features which increase the likelihood of fetal hypoxia. They include one or more of the following abnormal features: 2

20 A rising baseline or fetal tachycardia Reducing baseline variability Slow return to baseline FHR after a contraction Large amplitude (by 60bpm or to 60bpm) and/or long duration (60 sec) Loss of pre and post deceleration shouldering (abrupt increases in FHR baseline) Presence of post deceleration smooth overshoots (temporary increases in FHR above baseline) The physiological basis of decelerations is usually related to cord compression with subsequent changes in peripheral vascular resistance or oxygenation. Chemoreceptors and baroreceptors, found in the aortic arch and central nervous system, are sensitive to changes in blood chemistry and blood pressure. Increased CO 2 triggers the parasympathetic nervous system and results in a slowing of the fetal heart rate. When the umbilical cord is compressed or occluded there is an increase in fetal blood pressure. Animal studies suggest that the severity of variable decelerations is associated with the degree to which the cord is compressed, the duration of the compression or if there is total occlusion. Repetitive umbilical cord occlusions lead to an enhanced chemo-reflexic response as an adaptation to severe hypoxia. 14 Interpretation can be complicated since decreased arterial oxygen concentration, secondary to uteroplacental insufficiency from other causes, can also result in variable decelerations. Remember that one, single deceleration is meaningless and may be triggered by an immediate preceding event such as vaginal examination, change in maternal position, or rupture of membranes.

21 Late decelerations Late decelerations are defined as uniform and repetitive decreases in FHR which begin after the onset of the uterine contraction. Their nadir occurs more than 20 seconds after the peak of the contraction and ends after the contraction. 2 Late decelerations were originally attributed to uteroplacental insufficiency. Modern research has identified two different mechanisms known as non-asphyxial (reflex) or non-reflex, depending on the company that the decelerations keep. 15 During a contraction gaseous exchange within the intervillus space of the placenta is reduced. A vagal bradycardic response is initiated by chemoreceptor response to the transient hypoxaemia. In this setting, hypoxaemia is not immediate, as is a blood pressure change. This leads to the slow onset of the deceleration and hence the late definition. A previously well oxygenated fetus is able to return to normal metabolic status once the contraction recedes as it has been centrally well oxygenated; the heart, the brain and the adrenals have been spared. Late decelerations which occur in the company of decreased or absent variability indicate inadequate central oxygenation with little or no sparing, thus these babies are at risk of myocardial or cerebral hypoxia. These are more likely when there has been a chronic placental insufficiency. When associated with decreased variability or other FHR abnormalities there is an increased likelihood of significant fetal compromise and immediate evaluation and intervention are indicated. Subtle, shallow, late decelerations (<15 beats from the baseline), often associated with a nonaccelerative FHR pattern and reduced or absent variability, are clinically significant. These decelerations can be easily missed but often be detected by holding a straight edge (eg. a ruler) along the baseline.

22 Overall Assessment and Plan Having determined the risk, assessed the contractions and FHR pattern, an overall assessment of the situation and management plan should be made. The terms fetal distress and birth asphyxia are unhelpful and have no place in the assessment. The FHR tracing should be described as having normal or abnormal characteristics, or other specific terms that describe fetal acidaemia, hypoxia, and metabolic acidosis. Both RANZCOG 2 and NICE 1 recommend that common terms to describe patterns be established within a service so there is no misunderstanding between professionals about meaning. If the FHR pattern in labour is normal then a decision should be made regarding the method of fetal monitoring. Either an intermittent auscultative monitoring or CEFM technique can be employed. Consideration must be given to the clinical context and needs of the woman. CEFM may be necessary if identifiable risk factors of fetal hypoxia arise during labour. Documentation Documentation of fetal heart rate information during labour is required regardless of the monitoring technique used. Records may include narrative notes or flow sheets detailing the periodic assessments and should include information on the: FHR (ie. baseline rate, rhythm and nature of the changes) uterine activity characteristics from palpation and/or tocograph (e.g., frequency, duration, intensity and relaxation between contractions) specific actions taken if changes in the FHR occurred other maternal observations and assessments maternal and fetal responses to interventions any return to normal

23 Care should be taken in applying terminology used for CEFM when interpreting IA and should never include ambiguous terms such as hypoxia or asphyxia that are imprecise and non-specific. Considerations if an abnormal FHR pattern is detected A sudden decrease in fetal heart rate is often related to a specific event. It may be seen after vaginal examination, amniotomy, uterine hypertonus secondary to oxytocin, maternal hypotension secondary to an epidural, seizures, fetal scalp sampling, or fetal movement producing transient cord compression. If the fetus was not previously compromised, recovery will usually occur with discontinuation of the inciting event or agent, position change, increased intravenous fluids or a combination of these actions. Decelerations are more likely to be associated with fetal hypoxia when accompanied by a decreased baseline. Factors known to cause hypoxia should be sought and corrected. An abnormal FHR tracing may require the following action(s), each with close observation and reassessment: Change in method of monitoring. Assessment of maternal vital signs (temperature, blood pressure, pulse). Vaginal examination (checking for cord prolapse, vaginal bleeding, rapid descent of the head, and cervical dilatation). Discontinuation of oxytocin infusion. Acoustic or scalp stimulation (can induce accelerations and these are indicative of fetal wellbeing. However, failure to induce accelerations does not imply fetal compromise and further investigation should occur, eg fetal blood sampling) Maternal position change and intravenous fluids if hypovolaemia is suspected.

24 Tocolysis and plan immediate birth (assisted vaginal or caesarean). The following questions should be considered: Is this a gradually deteriorating pattern that may lead to a sudden decompensation if uncorrected? Is this a sudden drastic change with a cord prolapse? How much reserve does the baby have? Is this a term, low risk baby, or are there risk factors present such as growth restriction, postdates (suggest prolonged pregnancy >42 weeks or post term rather than postdates), hypertension, smoking, or meconium? Is assisted vaginal birth possible if the pattern does decompensate? Is this a multiparous woman who has progressed rapidly from six to nine centimetres? Is this a nulliparous woman early in labour? Management will often depend on an assessment of the risk of hypoxia and the ability to effect a rapid birth if necessary. If birth is imminent even severe decelerations are less significant than in the earlier stages of labour. Fetal Blood Sampling (FBS) Fetal blood sampling (FBS) is a technique used to provide a more accurate assessment of fetal wellbeing by measuring fetal metabolic acidosis by either determining ph or lactate in the fetal blood. Fetal heart rate monitoring is a screening test that provides reassurance if the FHR pattern is normal. However, if the FHR pattern is abnormal, the only way to truly assess fetal wellbeing is to perform FBS. FBS has been used over the last four decades but does have the disadvantage of being invasive to the woman and fetus and requires a relatively large amount of blood compared to that of lactate sampling. Fetal lactate has been found to have a strong correlation with cord arterial values and is

25 generally considered easier and less expensive than scalp ph sampling Fetal blood sampling is known to reduce the rates of intervention by identifying the fetus who requires this further intervention. Fetal blood sampling should ideally be available in all units who have ready access to the operating department. In the UK, it is recommended that all units who use CEFM have access to FBS. In Australia and New Zealand it is recognised that it may not be practicable for all maternity units in to have this facility. This is especially true of units where ready access to theatre is unavailable and where FBS may cause unnecessary delay in expediting the birth. 1 2 (Category C) Contraindications for FBS include clear evidence of continuous, serious abnormal FHR features, gestation less than 34 weeks, face presentation, fetal bleeding disorders such as suspected fetal thrombocytopaenia, maternal infections such as HIV, hepatitis, herpes simples or suspected uterine sepsis. 2 Lactate sampling When compared with scalp ph sampling, scalp lactate sampling has been shown to be as predictive as ph sampling with the benefits of requiring less blood, causing fewer scalp lacerations and being more likely to be successful. 23 For these reasons, many hospitals are choosing this method over ph sampling. During anaerobic metabolism, lactate levels can rise quickly and remain elevated where the hypoxic episode is prolonged. Lactate measures can be affected by venous stasis in the scalp and caput must be avoided as a sample site. During the procedure, care must be taken to avoid undue pressure on the scalp with the amnioscope as this can cause hypoperfusion of the sample site and produce artificially high lactate measures. 23 Lactate is known to increase with the duration of labour and particularly during active second stage. The evidence on lactate sampling in second stage is limited but it is generally not advised. It must also be considered that no matter how reassuring, a

26 single sample is meaningless if a FHR tracing remains abnormal. In this case the lactate should be repeated in 30 min to 1 hour. ph sampling Fetal blood is a direct measure of fetal acid-base balance in the blood. In the first stage of labour, during which a mild acidosis normally occurs, the mean fetal scalp blood ph is typically A ph value greater than 7.25 is considered to be normal. Values between 7.20 and 7.25 reflect a borderline or low normal situation. A ph below 7.2 is two standard deviations below the mean and is regarded as abnormal. During the second stage of labour a value as low as 7.15 may be acceptable provided normal progress is being made. The ph gives an indication of the immediate situation. When the fetal heart rate pattern is abnormal, only 50 to 65 percent of newborns are depressed as judged by the Apgar score, i.e. a 35 to 50 percent false positive rate. The false positive rate by scalp blood ph below 7.20 is only 10 to 20 percent. 4 A single sample, no matter how reassuring, means nothing if a FHR tracing remains abnormal. It is necessary to repeat the sample in half to one hour if the FHR tracing does not improve. The base excess provides an idea of fetal reserve. A value of less than -12 mmol/l should be treated as significant. Abnormal fetal acid-base balance is only one factor in the complex aetiology of cerebral palsy. MacLennan has suggested that three essential criteria must be fulfilled before intrapartum hypoxia can be considered the cause of subsequent cerebral palsy: 8 Evidence of metabolic acidaemia in intrapartum or very early neonatal blood samples (ph less than 7.00 and base excess less than -12 mmol/l).

27 Early onset of severe or moderate neonatal encephalopathy in infants of greater than, or equal to, 34 weeks gestation. Cerebral palsy of the spastic quadriplegic or dyskinetic type. Table 1: Comparison of fetal ph and lactate values during labour ph Lactate Interpretation Normal range Normal range Pre-acidotic- expedite birth Acidotic-Immediate birth Umbilical cord blood gas analysis Ideally, cord blood sampling of both umbilical arterial and umbilical venous blood is recommended. If only one sample is possible, it should be from the umbilical artery rather than the vein. 23 Umbilical arterial blood most accurately reflects fetal status because the umbilical artery flows directly from the fetus. In contrast, umbilical venous blood flows from the placenta to the fetus and better reflects maternal acid base status and placental function. Convincing arguments have been made for cord blood sampling at all high-risk births and whenever newborn depression occurs. Some would advocate for universal sampling at all births The medico-legal aspect of these arguments is based on the fact that most infants with cerebral palsy do not sustain insults in the peripartum period and have normal cord blood gases, while approximately one percent of vigorous infants have an umbilical arterial ph <7.10. Measuring lactate in a cord blood sample is now commonly used throughout

28 Australia as it has the dual benefits of requiring a smaller blood sample as well as being more cost effective. The sampling technique is simple and easily mastered by any team member in the birth suite. Preheparinised syringes ensure a consistent dose and amount of heparin. Normal ranges for umbilical cord blood gases vary (see Table 1). In general, the lower range for the arterial ph extends to at least 7.10 and for venous ph to at least A complete blood gas analysis may provide important information regarding the type and cause of acidaemia. Table 2: Normal umbilical cord blood gas values 25 Venous blood Arterial blood ph PCO PO Base excess HCO Areas for Future Development ST-analysis ST waveform analysis of fetal electrocardiogram (ECG) for intrapartum surveillance (known as STAN) is used in some European countries and the USA. Analysis of the fetal ECG wave during labour has been associated with reduced obstetric intervention for an abnormal fetal heart rate tracing in a high-risk pregnancy without jeopardising fetal outcome 26 (Category C). Guidelines and

29 recommendations concerning FHR pattern and ST waveform interpretation and classification were agreed on by the European experts on ST waveform analysis for intrapartum surveillance in There have been recorded cases which illustrate some of the drawbacks associated with the clinical application of the STAN technology which prevent severe metabolic acidosis being eradicated completely. 28 Further evaluation is ongoing and to date ST Waveform Analysis for the intrapartum assessment of an abnormal FHR pattern has not been recommended for routine use. 6 Computerised Cardiotocography Considerable evidence suggests that interpretation of the EFM is difficult and that mis-interpretation causes an increase in unnecessary intervention as well as being implicated in a large number of cases of birth asphyxia and avoidable perinatal mortality. 29 A system using artificial intelligence to interpret fetal monitor tracings is currently under development. 30 This uses a combination of clinical data and the fetal heart rate tracing to provide management options with the aim of identifying the fetus at risk of significant acidaemia while keeping the level of intervention as low as possible. Any system should be designed to support the decision-making of the clinician rather than replace it. Fetal Continuous Oxygen Monitoring Pulse oximetry may be another alternative to early identification of situations that require further evaluation. Further interventions may be reduced as long as the oxygen saturation and FHR pattern do not deteriorate. However, many factors adversely affect the accuracy of pulse oximetry including transducer placement, peripheral vasoconstriction, hypotension, anaemia, meconium staining, fetal hair and scalp oedema. 31 This method of monitoring is also limited by a wide normal range and inadequate calibration. 32 It has been shown to have no increased risk of maternal or fetal injury but has not lived up to early expectations as a fetal assessment tool. 33 Fetal pulse oximetry, with or without electronic fetal surveillance, is not recommended for routine use at this time. 6

30 Summary Initiation of fetal monitoring begins with assessment of maternal and fetal risk. As CEFM has a low positive predictive value and can result in increased rates of caesarean section, intermittent auscultation is recommended for low risk pregnancies. Staff availability and experience must be considered before deciding on this technique. Providers should be ready to change to CEFM if a highrisk situation develops. If CEFM is selected for fetal monitoring, interpretation needs to be done in light of the clinical background, the overall pattern, stage of labour, and in conjunction with fetal scalp or acoustic stimulation, or FBS. This combination maximises the benefit to the woman and her baby without increasing operative delivery rates. Outcomes may still be unaffected using this technique even in high-risk pregnancies. Regardless of which technology is employed the woman/support relationship is paramount during the labour process. Providers should not allow any monitoring approach to substitute for personal attention to the woman and her baby throughout labour. For each institution fetal monitoring methods should be utilised appropriately and standards maintained on a regular basis. Such standards should include keeping staff and clinicians up-to-date on any new developments as they arise. New technologies should be adequately reviewed and determined to be useful before being implemented.

31 Summary Table of Recommendations Category A The only clinically significant benefit from the use of routine CEFM is in the reduction of neonatal seizures. 6 The long-term benefits of this finding need to be evaluated. The decision to use intermittent auscultation versus CEFM should be made jointly by the woman and her provider. 1 Amnioinfusion for meconium stained fluid is associated with improvements in perinatal outcome particularly in settings where facilities for perinatal monitoring are limited. 34 Amnioinfusion for suspected cord compression appears to reduce the occurrence of variable heart rate decelerations and lower the use of caesarean delivery in those settings where caesarean delivery is done for abnormal fetal heart rate alone. 35 It should be noted that the studies on which this review is based are now quite old, and the technique of amnioinfusion for this indication is used quite infrequently in Australia. Category C The mnemonic DR C BRAVADO provides a systematic approach to the interpretation of FHR tracings for both CEFM and IA Auscultative monitoring is an acceptable monitoring method for women with low risk pregnancies. 1 Intermittent auscultation of the fetal heart after a contraction should occur for at least 1 minute, at least every 15 minutes, and the rate should be recorded as an average. The maternal pulse should be palpated if an FHR abnormality is detected to differentiate the two heart rates. 1 Women feel that their movement is restricted with EFM but their preference regarding monitoring method is less important than the support they receive from staff and companions. 3-5 Umbilical cord blood gas and ph values should be obtained after a high-risk birth and whenever newborn depression occurs. If only one vessel is selected it should be the umbilical artery rather than the vein. A complete blood gas analysis may provide important information regarding the type and cause of academia.

32 Category D Intermittent auscultation of the FHR is recommended for low-risk women in established labour in any birth setting. 1 Further guidance can be found at: National Institute for Health and Clinical Excellence Royal Australian and New Zealand College of Obstetricians and Gynaecologists: Updated by ALSO Asia Pacific Ltd September 2009 by the Fetal Monitoring Working Group Members: Karen Moffatt, Teoni McHale, Helen Cooke and Alison Green Edited by Alison Chandra, David Ellwood and Caroline Homer Approved by the ALSO Board September 2009 Further update March 2011 Helen Cooke and Caroline Homer

33 References 1. NICE. Intrapartum Care - Care of healthy women and their babies during childbirth. Clinical Guideline London: National Collaborating Centre for Women s and Children s Health, RANZCOG. Intrapartum Fetal Surveillance Clinical Guidelines. Second edition. Melbourne: Royal Australian and New Zealand College of Obstetricians and Gynaecologists, Luthy D, Shy K, van Belle G. A randomised controlled trial of electronic fetal monitoring in preterm labour (Level I). Obsterics and Gynecology 1987;69(5): MacDonald D, Grant A, Sheridan-Pereira M. The Dublin randomised controlled trial of intrapartum fetal heart rate monitoring (Level I). American Journal of Obstetrics & Gynecology 1985;152(5): Garcia J, Corry M, MacDonald D. Mother's views of continuous electronic fetal monitoring and intermittent auscultation: a randomised controlled trial. Birth 1985;12(2): Alfirevic Z, Devane D, Gyte G. Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour [Systematic Review]. Cochrane Database of Systematic Reviews 2006(Jul 19; 3: CD006066). 7. Liston R, Crane J. Featl Health Surveillance in Labour SOGC Clinical Practice Guidelines (no. 112). Montreal: Society of Obstetricians and Gynecoloists of Canada, MacLennan AH. A template for defining a causal relation between acute intrapartum events and cerebral palsy: international consenus statement (Level III). British Medical Journal 1999;319: ACOG. Intrapartum fetal heart rate monitoring. Obsterics & Gynecology 2005;106(6): The Consultative Council on Obstetric and Paediatric Mortality and Morbidity. Annual Report for the Year 2006, incorporating the 45th Survey of Perinatal Deaths in Victoria. Melbourne. Malbourne: Consultative Council on Obstetric and Paediatric Mortality and Morbidity, De Lange T, Budde M, Heard A, Tucker G, Kennare R, Dekker G. Avoidable risk factors in perinatal deaths: A perinatal audit in South Australia. Australian and New Zealand Journal of Obstetrics and Gynaecology 2008;48: Steer P. Has electronic fetal heart rate monitoring made a difference?. Seminars in Fetal and Neonatal Mediine 2008;13: King T, Parer J. The physiology of fetal heart rate patterns and perinatal asphyxia. Journal of Perinatal and Neonatal Nursing 2000;14(3): Bennet L, Westgate J, Yung-Chi L, Wassink G, Gunn A. Fetal acidosis and hypotension during repeated unbilical cord occlusions are associated with enhanced chemoreflex responses in near-term fetal sheep. Journal of Applied Physiology 2005;99: Parer J. Handbook of Fetal Heart Rate Monitoring 2nd ed. Philadelphia WB Saunders Company, CESDI. Confidential Enquiry into Stillbirths and Deaths in Infancy: 8th Annual Report, London Maternal and Child Health Research Consortium, Neldam S, Osler M, Hansen P. Intrapartum fetal heart rate monitoring in a combined low-and high-risk population: a controlled clinical trial (Level I) European Journal of Obstetrics & Gynaecology 1986;23: Beard R, Filshie G, Knight C, Roberts G. The significance of the changes in the continuous fetal heart rate in the first stage of labour (Level III). J Obstet Gynaecol Br Commnwlth 1972;78(10): Whittle M, editor. The management and monitoring of labour (Level III). 2nd ed. Edinburgh: Churchill Livingstone, 1995.

34 20. Spencer J, Ward R. Intrapartum Fetal Monitoring (Level III). In: RCOG, editor. 26th RCOG Study Group. London: RCOG Press, Ingemarsson I, Ingemarsson E, Spencer J. Fetal Heart Rate Monitoring - A Practical Guide (Level III). Oxford: Oxford University Press, Simpson K, Dotti J. Effects of oxytocin-induced uterine hyperstimulation during labor on fetal oxygen status and fetal heart rate patterns. American Journal of Obstetrics & Gynecology 2008;199(1):34e1-34e Allen R, Bowling F, Oats J. Determining the fetal scalp lactate level that indicates the need for intervention in labour. Australian and New Zealand Journal of Obstetrics and Gynaecology 2004;44: Thorp J, Rushing R. Umbilical cord blood gas analysis (Level III). Obstetrics and Gynecology Clinics of North America 1999;26(4): Pomerace J. Umbilical cord blood gases casebook (Level III). Journal of Perinatology 2000;5: Neilson J. Fetal electrocardiogram (ECG) for fetal monitoring during labour. Cochrane Database of Systematic Reviews 2009; Issue 2(Art. No.: CD000116). 27. Liston R, Sawchuck D, Young D. Fetal Health Surveillance: Antepartum and Intrapartum Consensus Guideline (No 197). Journal of Obstetrics and Gynaecology Canada 2007;29(9):S25-S Amer-Wahlin I, Arulkumaran S, Hagberg H, Maršál K, Visser G. Fetal electrocardiogram: ST waveform analysis in intrapartum surveillance. BJOG 2007;114: Diller L. Babies' death linked to sub-optimal care. BMJ 1995;310: Greene K,.. Intelligent fetal heart rate computer systems in intrapartum monitoring (Level III). Current Opinion in Obstetrics & Gynecology 1996;8(2): Elachalal U, Weissman A,. Intrapartum fetal pulse oximetry: present and future (Level III). International Journal of Gynaecology & Obstetrics 1995;50(2): Maesel A, Martensson L. Fetal pulse oximetry. A methodological study.(level III). Acta Obstetricia et Gynecologica Scandinavica 1996;75(2): Luttkus A, Friedmann W. The safety of fetal pulse oximetry in parturients requiring fetal scalp blood sampling (Level II-2). Obstetrics & Gynecology 1997;90(4 Pt 1): Hofmeyr G. Amnioinfusion for meconium-stained liquor in labour. Cochrane Database of Systematic Reviews 2001;Issue 4.(Art. No.: CD000014). 35. Hofmeyr G. Amnioinfusion for potential or suspected umbilical cord compression in labour. Cochrane Database of Systematic Reviews 1998;Issue 1:Art. No.: CD DOI: / CD

35 Intra-partum Fetal Monitoring Objectives Review evidence regarding continuous electronic fetal monitoring (CEFM) Identify key factors in use of intermittent auscultation (IA) versus CEFM Utilise the mnemonic DR C BRAVADO Develop plan based on overall assessment of mother and baby Significance of fetal heart rate FHR pattern is an indirect measure of fetal acid-base status FHR pattern reflects carotid and aortic, vagal, chemoreceptor, and baroreceptor response to oxygen, ph, CO 2, arterial pressure. 1

36 Antenatal Indications for CEFM Abnormal antenatal CTG or Doppler flow studies Suspected or confirmed growth restriction Oligohydramnios or polyhydramnios Prolonged pregnancy: > 42 weeks Multiple pregnancy Breech presentation Antenatal Indications for CEFM Antepartum haemorrhage Prolonged rupture of membranes Previous uterine scar/lscs Pre-eclampsia Diabetes (on insulin or poorly controlled with fetal macrosomia) Other current or previous obstetric or medical conditions which constitute a significant risk of fetal compromise Intrapartum Indications for CEFM Induction or augmentation of labour Abnormal fetal heart rate on auscultation or CTG Epidural analgesia Abnormal vaginal bleeding in labour Maternal pyrexia > 38C 2

37 Intrapartum Indications for CEFM Liquor: absent, blood-stained, or meconium stained Active 1 st stage > 12 hrs Active 2 nd stage (pushing) > 1 hr where birth is not imminent Preterm labour < 37 completed weeks Outcomes With CEFM 12 randomised controlled trials of > 58,000 births: No difference in 1 min. APGAR score <7 Slight decrease in neonatal seizures No difference in NICU admission rates Increased rate of caesarean and operative vaginal delivery, especially in women with low-risk pregnancies Intermittent auscultation IA Doppler signal on speaker mode Auscultation should commence at end of contraction IA continue for at least 30 seconds after cessation of the contraction 3

38 IA Frequency At least every minutes in active phase of first stage At least every 5 minutes in the second stage of labour DR C BRAVADO Determine Risk Contractions Baseline Rate Variability Accelerations Decelerations Overall assessment & plan DR = Determine Risk Antenatal risk factors Intrapartum risk factors Fetal reserve Labour progress 4

39 C = Contractions Method of monitoring Palpation External transducer Pattern and intensity Adequate Hyper-stimulation (>7 in 15 min) BRA = Baseline RAte Requires >10 minutes to establish Normal = beats per min IA - determine between contractions Baseline rate influenced by: Prematurity Change in fetal status Maternal fever, position, medication V = Variability Normal = 5-25 bpm around baseline (peak to trough fluctuation over 1 min of trace) Reflects normal CNS function Best predictor of good fetal outcome Most accurately assessed with fetal scalp electrode 5

40 Causes of Decreased Variability Hypoxia / acidosis Fetal sleep cycle Prematurity Congenital anomalies (CNS) Drugs nervous system depressants anticholinergics / parasympatholytics corticosteroids A = Accelerations Definition Increase of > 15 bpm above baseline Last > 15 seconds Presence indicates fetal well-being Absence Frequently false positive in low risk patients Further evaluation required 6

41 D = Decelerations Definition Decrease of > 15 bpm below baseline Last > 15 seconds Requires correlation to contraction pattern Classification impossible with IA appropriate to consider CEFM D = Decelerations (RANZCOG) Early Variable Complicated variable Prolonged Late Early decelerations Uniform, repetitive, periodic slowing of FHR Onset early in the contraction Return to baseline by the end of the contraction Are a result of head compression Are benign 7

42 Late decelerations Uniform, repetitive, periodic slowing of FHR with slow onset mid to end of the contraction Nadir more than 20 seconds after the peak of the contraction and Ends after the contraction In the presence of a non-accelerative trace, with baseline variability less than 5 bpm, the definition would include decelerations less than 15 bpm Late decelerations Reflect a change in placental ability to meet fetal needs adequately May reflect fetal hypoxia and acidosis 8