Newborn Outcomes in British Columbia After Caesarean Section for Non-Reassuring Fetal Status

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1 OBSTETRICS Newborn Outcomes in British Columbia After Caesarean Section for Non-Reassuring Fetal Status Kevin Jenniskens, MSc, 1,2 Patricia A. Janssen, PhD 2,3 1 Radboud University Nijmegen Medical Centre, Institute for Health Sciences, Nijmegen, The Netherlands 2 School of Population and Public Health, University of British Columbia, Vancouver BC 3 Child and Family Research Institute, Vancouver BC Abstract Objective: To assess the incidence in British Columbia of severe morbidity in neonates delivered by Caesarean section for nonreassuring fetal status, and to examine the accuracy of Apgar score and umbilical cord gas values in predicting severe neonatal morbidity. Methods: We assessed rates of hypoxic ischemic encephalopathy, NICU admission, and ventilator days, individually and as a composite outcome with neonatal death, among a total of 8466 term singletons delivered by Caesarean section for non-reassuring fetal status between January 1, 7, and December 31, 11. We calculated the predictive accuracy of Apgar scores and umbilical cord blood gas values using the area under the receiver operating characteristic (ROC) curve and the sensitivity and specificity for each outcome. Results: The incidence of Apgar score at one minute < 4 was 8.%, and for Apgar score at five minutes < 4 it was.6%. The incidence of umbilical cord ph < 7. was 6.5%, and for base-excess < 12 it was 2.9%. Apgar score at one minute < 7 had the greatest predictive accuracy for the composite outcome (81% for both sensitivity and specificity). The area under the ROC curve for Apgar score at one minute and at five minutes, umbilical cord ph, and base-excess was.87,.86,.76, and.78, respectively. Conclusion: The incidence of abnormal Apgar score and abnormal umbilical cord gas values is very low among neonates in British Columbia delivered by Caesarean section for non-reassuring fetal status. Apgar score at one minute < 7 is a good predictor of severe neonatal morbidity. Electronic fetal monitoring remains a non-specific method for detection of fetal compromise in the intrapartum period. J Obstet Gynaecol Can 15;37(3):7 213 Key Words: Apgar score, Caesarean section, fetal distress, sensitivity, specificity, umbilical cord blood Competing Interests: None declared. Received on April 14, 14 Accepted on October 1, 14 Résumé Objectif : Évaluer l incidence (en Colombie-Britannique) de la morbidité grave chez les enfants nés par césarienne en raison d un état fœtal non rassurant et examiner la précision de l indice d Apgar et des valeurs de la gazométrie du cordon ombilical pour ce qui est de la prévision de la morbidité néonatale grave. Méthodes : Nous avons évalué le taux d encéphalopathie hypoxique ischémique, le taux d admission à l UNSI et le nombre de jours de soutien au moyen d un appareil à ventilation artificielle, de façon individuelle et sous forme d issue composite conjointement avec le décès néonatal, chez un total de enfants étant nés à terme à la suite d une grossesse monofœtale accouchée par césarienne en raison d un état fœtal non rassurant entre le 1 er janvier 7 et le 31 décembre 11. Nous avons calculé la précision prévisionnelle des indices d Apgar et des valeurs de la gazométrie du cordon ombilical au moyen de la surface sous la courbe de la fonction d efficacité du récepteur (ROC), ainsi qu au moyen de leur sensibilité et de leur spécificité pour chacune des issues. Résultats : L incidence de l obtention d un indice d Apgar à une minute < 4 était de 8, %, tandis qu elle était de,6 % pour ce qui est de l indice d Apgar à cinq minutes < 4. L incidence de l obtention d un ph de cordon ombilical < 7, était de 6,5 %, tandis que l incidence de l obtention d un excès basique < 12 était de 2,9 %. L indice d Apgar à une minute dont la valeur était < 7 constituait le paramètre disposant de la meilleure précision prévisionnelle pour ce qui est de l issue composite (81 %, tant pour la sensibilité que pour la spécificité). Les surfaces sous la courbe ROC en ce qui concerne les indices d Apgar à une minute et à cinq minutes, le ph du cordon ombilical et l excès basique étaient de,87, de,86, de,76 et de,78, respectivement. Conclusion : L incidence de l obtention d un indice d Apgar anormal et de valeurs anormales de gazométrie du cordon ombilical est très faible en Colombie-Britannique chez les enfants nés par césarienne en raison d un état fœtal non rassurant. L indice d Apgar à une minute dont la valeur est < 7 constitue un bon facteur prédictif de la morbidité néonatale grave. Le monitorage fœtal électronique demeure une méthode non spécifique en ce qui concerne la détection d un danger grave pour le fœtus pendant la période intrapartum. MARCH JOGC MARS 15 7

2 Obstetrics INTRODUCTION The Caesarean section rate in Canada increased from 22.5% in 1 to 27.1% in 11. 1,2 Similar trends were observed in the province of British Columbia, which in 11 had the highest total and primary provincial CS rates in Canada, at 32.% and 22.4%, respectively. 2 The Public Health Agency of Canada has attributed the rise in rates of CS in part to increased use of electronic fetal monitoring. 3 EFM is known to have a high rate of false indication of abnormality, resulting in potentially unnecessary CS for non-reassuring fetal status (formerly known as fetal distress or non-reassuring fetal heart rate). 4 CS is not without risk, both for mother and fetus. Adverse events for the newborn include lacerations during the procedure and respiratory distress. 5 7 Maternal complications include infection of the surgical wound, thrombosis, hemorrhage, surgical injury to other organs, complications related to anaesthesia, and abnormal placentation in subsequent pregnancies. 6 9 A study by Declerq et al. showed that 78% of women who delivered by CS had a hospital stay of at least three days, compared to % of women who delivered vaginally. A longer hospital stay and re-admission to hospital after CS incur higher costs to the health care system. 3,11,12 In a 13 study, Declerq et al. reported that, during the first two months after delivery, pain interfered with daily activities significantly more in women who had a CS than in women who had a vaginal delivery. 13 In this study, 19% of women who delivered by CS described incisional pain as a major problem, and 16% reported ongoing pain until at least six months after CS. 13 NRFS is among one of the most prevalent indications for primary CS. 14,15 EFM remains the primary instrument used to assess fetal status in labour. It records fetal heart rate patterns, uterine contractions, and fetal movements. 16 The Society of Obstetricians and Gynaecologists of Canada revised their recommendations for diagnosis and management of atypical and abnormal EFM tracings, formerly known as NRFS, in their 7 clinical practice guideline Fetal Health Surveillance. 17 EFM has proven to ABBREVIATIONS AUC BC EFM FHR HIE NRFS ROC area under the curve British Columbia electronic fetal monitoring fetal heart rate hypoxic ischemic encephalopathy non-reassuring fetal status receiver operating characteristic have limited intra-observer and inter-observer reliability The use of computerized scoring systems has been proposed to reduce variability in interpretation among clinicians, but has not reduced the CS rate. 22,23 The capacity of EFM to predict Apgar score and umbilical cord blood gas values recorded at birth varies widely across studies, especially among newborns delivered by CS for NRFS. 24 The National Institute for Health and Care Excellence in the United Kingdom has called for large-scale studies to assess the capacity of EFM to predict outcomes such as cord blood gas values and Apgar scores, as well as longer term outcomes such as hypoxic ischemic encephalopathy, respiratory problems, and duration of NICU admission. 31 This recommendation was repeated in a Cochrane review in. 32 We sought to determine the incidence of severe morbidity in neonates in British Columbia delivered by CS for NRFS, and to evaluate the accuracy of Apgar score and umbilical cord gas variables in predicting these adverse events. METHODS We conducted a retrospective cohort study utilizing data from the Perinatal Services BC data registry for January 1, 7, to December 31, 11. The study cohort consisted of 8466 neonates delivered by CS for NRFS. Cases were born to women in British Columbia with a singleton pregnancy, a gestational age between 37 and 41 weeks at delivery, and delivery by emergency CS for the indication of NRFS. Atypical and abnormal EFM tracings were defined by the Society of Obstetricians and Gynaecologists of Canada in the 7 guidelines. 17 Intrapartum electronic fetal monitoring tracings are described in the guideline as normal, atypical, or abnormal according to a set of criteria for baseline FHR and FHR variability, decelerations, and accelerations. Gestational age was determined using an algorithm 33 that takes into account the date of the last menstrual period, findings on early ultrasound (before weeks), the findings on clinical examination of the newborn, and the estimate of gestational age documented in the chart. Gestational age was calculated in completed weeks. For analysis of capacity to predict neonatal morbidity, we assessed cut-off Apgar scores < 4 and < ,28 A newborn with an Apgar score < 7 is considered to require immediate medical attention, but a score of < 4 is critically low. 34 To predict morbidity arising from an acidotic state, we analyzed the data using cut-off values for umbilical cord artery ph of 7., 7.15, and ,27,29,35 Umbilical cord arterial base excess cut-off values were set at 8 and Negative base excess indicates metabolic acidosis MARCH JOGC MARS 15

3 Newborn Outcomes in British Columbia After Caesarean Section for Non-Reassuring Fetal Status We defined severe adverse outcomes as admission to a level III NICU for two days or more, requirement of ventilator support, and diagnosis of HIE. Until April 1,, level III NICU stay was calculated using the number of days a newborn occupied an NICU bed. Thereafter, it was defined as the number of days that a newborn received level III care as stated by the Perinatal Services BC Neonatal Levels of Service Classification. HIE was diagnosed using the International Classification of Diseases, th Edition, Canada diagnosis code P91.6. A composite outcome variable was computed if any of the above variables were present or death was recorded within 28 days of birth. (the proportion of true positives) and specificity (the proportion of true negatives) were calculated using SPSS v. 21 (IBM Corp., Armonk, NY). Predictive accuracy was calculated as the mean of sensitivity and specificity. Confidence intervals were calculated using the Wilson score method without continuity correction. 41 Receiver operating characteristic curves were generated and the area under these curves was calculated to determine the performance of the predictors for severe adverse outcomes. The value for AUC ranges from.5 (no better than chance) to 1. (perfect predictor). Scores are qualitatively defined as poor (AUC <.7), fair (.7 < AUC <.8), good (.8 < AUC <.9), and excellent (.9 < AUC < 1.). 42 Coordinate points of the ROC curve were imported in Microsoft Excel (Microsoft Corp., Redmond, WA) to generate graphs for sensitivity and specificity. This study was approved by the Clinical Ethics Board at the University of British Columbia. RESULTS The distribution of gestational ages ranged from 8.% delivered at 37 weeks to 32.1% delivered at weeks (Table 1). One in five women was multiparous. Most Caesarean sections were performed at large hospitals, with only 8.9% giving birth at the smallest hospitals (< 5 births per year). The average maternal age was.9 years, consistent with 11 Statistics Canada data. 43 The mean Apgar scores and umbilical cord gas values were within the normal range. The incidence of Apgar score at one minute < 7 was 19.9%, and of Apgar score at five minutes < 7 was 3.9%. Umbilical cord ph < 7. and base-excess < 8 were present in 23.7% and.8% of neonates, respectively. HIE was diagnosed in 35 neonates delivered by CS for NRFS (Table 2). The sensitivity of Apgar scores, umbilical cord ph, and base excess for predicting HIE varied from 34% (using Apgar score at 5 minutes < 4) to 9% Table 1. Sociodemographic characteristics Caesarean section for non-reassuring fetal Descriptives status (n = 8466) Gestational age, weeks, n (%) (8.) (14.5) (24.3) 2715 (32.1) (21.1) Parity, n (%) Nulliparous 6723 (79.4) Multiparous 1743 (.6) Hospital size,* n (%) < (3.2) 25 to (5.7) 5 to (12.) to (.2) (39.) Maternal age, years, mean (SD).9 (5.63) Apgar score at 1 minute (n = 8463) mean (SD) 7.63 (2.9) < 4 68 (8.%) < (19.9%) Apgar score at 5 minutes (n = 8458) mean (SD) 8.87 (1.4) < 4 5 (.6%) < 7 3 (3.9%) Umbilical cord ph (n = 7193) mean (SD) 7.24 (.9) < (6.5%) < (12.6%) < (23.7%) Base excess (n = 6516) mean (SD) 3.64 (4.5) < 8 71 (.8%) < (2.9%) *Number of mothers who delivered a child and were discharged during the 7/8 fiscal year. (using umbilical cord ph < 7.). The sensitivity of these variables to predict level III NICU stay 2 days did not exceed 57%. Ventilator days were best predicted by Apgar score at one minute < 7 (sensitivity 89%, specificity 8%). The composite outcome of severe morbidity was present in 178 cases (2.1%). This included 15 neonatal deaths. Four required ventilator support and one developed HIE. Apgar score at one minute < 7 most accurately predicted the composite outcome (81%). None of the possible combinations of the predictors studied provided better predictive accuracy than Apgar score at one minute < 7 (results not shown). Apgar scores were more reliable MARCH JOGC MARS 15 9

4 Obstetrics Table 2. and specificity (95% CI) of predictors for severe adverse outcomes* Hypoxic ischemic encephalopathy (n = 35) NICU level III stay 2 days (n = 62) Ventilator days (n = 126) Composite severe outcome (n = 178) Predictors (%) (%) (%) (%) (%) (%) (%) (%) Apgar score 1 minute < 4 8 (64 to 9) 92 (92 to 93) 31 (21 to 43) 92 (92 to 93) 68 (6 to 76) 93 (92 to 93) 6 (53 to 67) 93 (93 to 94) 1 minute < 7 89 (74 to 95) 8 (79 to 81) 57 (44 to 68) 8 (79 to 81) 89 (82 to 93) 81 (8 to 82) 81 (75 to 86) 81 (81 to 82) 5 minutes < 4 34 (21 to 51) (99 to ) (5 to ) (99 to ) 21 (15 to 29) ( to ) 21 (16 to 28) ( to ) 5 minutes < 7 77 (61 to 88) 96 (96 to 97) 32 (22 to 45) 96 (96 to 97) 65 (56 to 73) 97 (97 to 98) 57 (49 to 64) 97 (97 to 98) Umbilical cord ph < (47 to 8) 94 (93 to 94) 29 (18 to 45) 94 (93 to 94) (31 to 49) 94 (93 to 95) 38 (31 to 46) 94 (94 to 95) < (65 to 92) 88 (87 to 88) 39 (26 to 52) 88 (87 to 88) 52 (42 to 61) 88 (87 to 89) 5 (42 to 58) 88 (87 to 89) < 7. 9 (74 to 96) 77 (76 to 78) 56 (42 to 68) 77 (76 to 78) 62 (53 to 71) 77 (76 to 78) 63 (55 to 7) 77 (76 to 78) Base excess < 8 mmol/l 81 (62 to 91) 9 (89 to 9) 39 (27 to 53) 89 (89 to 9) 53 (43 to 62) 9 (89 to 91) 49 ( to 57) 9 (89 to 91) < 12 mmol/l 62 (43 to 78) 97 (97 to 98) (11 to 32) 97 (97 to 98) 31 (23 to 41) 98 (97 to 98) 29 (22 to 37) 98 (97 to 98) * and specificity were rounded to whole percentages. Composite severe outcome is defined by the presence of hypoxic ischemic encephalopathy, NICU level III stay 2 days, ventilator days, or neonatal death. Table 3. Area under the ROC curve with 95% confidence intervals for predictors of severe outcomes Hypoxic ischemic encephalopathy (n = 35) NICU level III stay 2 days (n = 62) Ventilator days (n = 126) Composite severe outcome* (n = 178) Predictors Apgar score 1 minute.92 (.87 to.97).72 (.66 to.79).91 (.88 to.94).87 (.84 to.9) Apgar score 5 minutes.94 (.89 to.99).73 (.66 to.8).91 (.88 to.94).86 (.82 to.89) Umbilical cord ph.91 (.84 to.98).74 (.66 to.81).75 (.69 to.81).76 (.71 to.81) Base excess.94 (.91 to.97).75 (.69 to.81).78 (.72 to.83).78 (.73 to.82) *Composite severe outcome is defined by the presence of hypoxic ischemic encephalopathy, NICU level III stay 2 days, ventilator days, or neonatal death. 2 MARCH JOGC MARS 15

5 Newborn Outcomes in British Columbia After Caesarean Section for Non-Reassuring Fetal Status and specificity of predictors for the composite severe outcome at different cut-off values Apgar < 4 Apgar < Apgar score at 1 minute Apgar < 4 Apgar < Apgar score at 5 minutes ph < 7. ph < 7.15 ph < BE < -12 BE < -8 Umbilical cord blood ph Base-excess in mmol/l predictors of the composite severe outcome than umbilical cord gas values, as shown in Table 3. All variables showed excellent capacity to predict HIE (AUC >.9), but only fair capacity to predict NICU stay (AUC <.8). Apgar scores were significantly better at predicting ventilator days than umbilical cord gas values. All AUC scores were significantly different from an AUC of.5. The choice for cut-off value of a predictor has consequences for sensitivity and specificity for a severe outcome. Curves for sensitivity and specificity of Apgar scores, umbilical cord ph, and cord arterial base excess are shown in the Figure, with the selected cut-off values. A higher cut-off value for each predictor in each case resulted in lower specificity and higher sensitivity. This trade-off was approximately equal for Apgar score at one minute, umbilical cord ph, and base excess. The specificity of Apgar at five minutes < 7 was similar to Apgar score at five minutes < 4, while sensitivity was nearly three times higher. DISCUSSION We found that most neonates in British Columbia delivered by emergency CS for NRFS did not have abnormal Apgar scores or umbilical cord gas values. The proportion of neonates with these abnormal outcomes is slightly lower than in previous reports. 28 Among newborns delivered by CS for NRFS, Apgar scores predicted severe adverse outcomes better than umbilical cord gas values. The best overall predictor for our composite severe outcome was Apgar score at one minute < 7, which had both a sensitivity and a specificity of 81%. Obwegeser et al. found in a retrospective study that Apgar score at five minutes 7 was a better predictor of poor outcomes in newborns than umbilical cord ph < This finding is noteworthy, since the purpose of Apgar scores is to identify newborns requiring immediate care rather than to predict long-term neurological or developmental outcomes. 45 Apgar scores and cord blood gas values had the lowest sensitivity for predicting NICU stay (< 6%), most likely because hypoxia during pregnancy is only one of various factors contributing to NICU stay. Apgar scores were better than umbilical cord gas values at predicting our composite outcome, mainly because of higher accuracy in predicting ventilator days (Table 3). There are several alternatives to EFM for fetal surveillance, but they are not always appropriate to use. Fetal scalp blood sampling has been considered an ideal method of detecting fetal hypoxia in utero. 46 Fetal scalp blood ph and lactate level correlate significantly with umbilical cord blood base deficit, ph, and lactate level, as well as with each other Fetal scalp blood lactate measurement is preferred to ph because it requires a smaller blood sample, MARCH JOGC MARS

6 Obstetrics a shorter sampling time, and a significantly lower rate of failure. 48,5,51 Point of care devices for measuring lactate levels are affordable, accessible, and show good correlation with laboratory reference standards. 52,53 Fetal scalp lactate measurement does have several limitations, including the requirement for cervical dilatation of at least 3 cm, for ruptured membranes, and for the availability of point of care equipment, as well as a trained attendant. 54,55 Fetal scalp blood lactate measurement is contraindicated in women who have infections. (e.g., HIV, hepatitis, or herpes simplex virus), and it correlates poorly with Apgar scores. 48,55,56 Fetal scalp lactate measurement is performed ideally during the first stage of labour, due to the relatively constant lactate concentration during this period. 57 However, hypoxic events have been shown to occur mostly during the second stage of labour, when lactate concentrations can vary greatly. 58,59 The SOGC has recommended against the use of fetal pulse oximetry and ST waveform analysis as alternatives for screening for fetal hypoxia. 17 They also suggest that use of fetal artery Doppler monitoring is warranted only under specific conditions. 17 Assessment of compliance with the SOGC s 7 guidelines on fetal surveillance 17 for appropriate diagnosis and subsequent decision-making will be necessary to validate the recommendations made, and to consider whether changes in adherence to the guidelines could improve the ability of EFM to predict the need for emergency CS. A study by Valentin et al. showed that late FHR decelerations, absence of variability in FHR, and bradycardia have different capacities to predict abnormal Apgar scores. 24 Future studies should include consideration of these observations, and should also consider stratifying the data on HIE grades as defined by the Sarnat criteria, 6 since only Sarnat grades 2 and 3 are associated with hearing impairment, severe disability, or death CONCLUSION EFM during labour does not specifically identify neonates at risk for morbidity at birth (as defined by Apgar scores or umbilical cord blood parameters). The prevalence of abnormal Apgar scores at five minutes or abnormal umbilical cord gas ph or base excess values among neonates delivered by CS for NRFS is less than %, suggesting that the number of Caesarean sections performed for this indication could be safely reduced; doing so would prevent the associated maternal morbidity and costs. 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