Clinical Significance of First Trimester Umbilical Cord Cysts

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1 Clinical Significance of First Trimester Umbilical Cord Cysts Waldo Sepulveda, MD, Sergio Leible, MD, Angel Ulloa, MD, Milenko Ivankovic, MD, Carlos Schnapp, MD A cystic mass of the umbilical cord was identified by transvaginal sonography in 10 first trimester pregnancies at a mean gestational age of 8 weeks 4 days (range, 8 weeks 1 day to 9 weeks 3 days) and at a mean crown-rump length of 20.5 mm (range, 15 to 25 mm). The cyst was solitary in all cases, the mean diameter was 4.6 mm (range, 3 to 6 mm), and the location was closer to the fetal insertion in two cases, in the middle of the cord in seven cases, and closer to the placental insertion in one case. Gestational sac and yolk sac diameters as well as the fetal heart rate were within normal ranges for gestational age in all cases. Information on detailed second trimester scans was available in nine cases, demonstrating complete resolution of the cyst and normal fetal anatomic survey in each case. These nine pregnancies were followed to delivery, and normal healthy infants were delivered at term in all cases. This series suggests that the incidental detection of umbilical cord cysts in early pregnancy is not associated with an adverse pregnancy outcome. KEY WORDS: Umbilical cord; Cyst, umbilical cord; Prenatal sonography. Cystic masses are among the most common sonographically detectable abnormalities of the umbilical cord. 1,2 Most SD, Standard deviation ABBREVIATIONS Received July 20, 1998, from the Fetal Medicine Center, Department of Obstetrics and Gynecology (W.S., M.I., C.S.), Clinica Las Condes, Santiago; the Department of Obstetrics and Gynecology (S.L.), Jose Joaquin Aguirre Hospital, Santiago; and the Ultrasound Diagnostic Center (A.U.), Rancagua, Chile. Revised manuscript accepted for publication September 22, Address correspondence and reprint requests to Waldo Sepulveda, MD, Fetal Medicine Center, Clinica Las Condes, Casilla 268, Santiago 34, Chile. cases are diagnosed during the second or third trimester, a time at which the association with fetal structural anomalies and chromosomal disorders is well documented in the literature Prenatal diagnosis of umbilical cord cysts in the first trimester by means of transvaginal sonography also has been reported However, information on the clinical significance of this sonographic finding in early pregnancy is scarce and controversial. Indeed, initial reports described first trimester umbilical cord cysts as transient and with no effect on pregnancy outcome, 11,12 but recently these cysts have been associated with fetal structural anomalies and chromosomal defects in up to 26% of the cases. 13 The aim of this study was to report our experience with 10 cases of umbilical cord cysts detected in the first trimester in an attempt to determine their natural history and clinical significance by the American Institute of Ultrasound in Medicine J Ultrasound Med 18:95 99, /99/$3.50

2 96 FIRST TRIMESTER UMBILICAL CORD CYSTS J Ultrasound Med 18:95 99, 1999 MATERIALS AND METHODS During the 18 month period from October 1996 to March 1998, an umbilical cord cyst was diagnosed during prenatal sonography in 10 first trimester fetuses evaluated at three obstetric ultrasound units. Sonography was performed transvaginally with a variety of types of commercially available ultrasound equipment using 5.0 to 7.0 MHz curved array transvaginal probes. The crown-rump length, diameters of the gestational sac and yolk sac, and fetal heart rate were evaluated routinely in each case as part of our routine first trimester scanning protocol. Gestational age was determined by menstrual dates and confirmed by crown-rump length measurement at the time of the scan. If the difference between dates and crown-rump length was more than 5 days, the sonographic estimation was used for analysis. Umbilical cord cyst was diagnosed when a round, thin-walled anechoic structure was identified within the amniotic cavity, in close connection to the umbilical cord and separate from the fetal pole and physiologic hernia. The cyst was clearly distinguishable from the yolk sac, which had a more echoic wall and was extraamniotic in location (Fig. 1). Color Doppler imaging was used to exclude the possibility of an umbilical cord aneurysm 14 and to document the relation with the umbilical vessels (Fig. 2). Follow-up scans were obtained at the discretion of the referring obstetrician, but a comprehensive anatomic survey for fetal structural anomalies at 18 to 22 weeks gestation was recommended to all women. Information on gestational age at diagnosis, indication for the scan, prenatal sonographic findings, follow-up scans, and pregnancy outcome was obtained by chart review or by contacting the referring obstetrician. the placental insertion in the remaining case. Gestational sac measurements, yolk sac diameter, and fetal heart rate were within the normal range for gestational age in all cases. Umbilical blood flow velocity waveforms were obtained from the proximal segment of the cord in six pregnancies, demonstrating the expected pattern of absent end diastolic flow in the umbilical artery 15 and pulsation in the umbilical vein 16 in all of these cases (Fig. 3). One woman did not return for evaluation and was lost to follow-up. Of the remaining nine pregnancies, six women underwent follow-up scanning between 12 and 14 weeks gestation; resolution of the cyst was documented in each case. Comprehensive fetal anatomic survey performed at 18 to 22 weeks gestation demonstrated normal appearance of the umbilical cord and normal fetal anatomy in all nine cases. These nine pregnancies were followed to delivery; healthy normal infants were delivered at term, and postpartum examination of placenta and umbilical cord showed no gross abnormality. DISCUSSION This report describes 10 cases of umbilical cord cyst detected by transvaginal sonography in the first trimester. In keeping with previous observations, 11,12 this sonographic finding was identified at 8 to 9 weeks gestation and resolved spontaneously in all cases. First trimester umbilical cord cysts were first Figure 1 Transvaginal sonogram at 8 weeks 4 days shows umbilical cord cyst (open arrow). Note that the yolk sac (solid arrow) has a more echoic wall and is clearly seen to be separate from the cyst. RESULTS Table 1 shows the principal clinical and sonographic findings in our 10 cases. Primary reason for referral was confirmation of dates in all cases. All women were asymptomatic at the time of the scan, and only one was older than 35 years. The diagnosis of umbilical cord cyst was made at a mean gestational age of 8 weeks 4 days (range, 8 weeks 1 day to 9 weeks 3 days) and at a mean crown-rump length of 20.5 mm (SD, 3.3; range, 15 to 25 mm). In all cases the umbilical cord cyst was single and measured from 3 to 6 mm (mean, 4.6 mm; SD, 1.1). The cyst was located closer to the fetal insertion in two cases, in the middle of the cord in seven cases, and closer to

3 J Ultrasound Med 18:95 99, 1999 SEPULVEDA ET AL 97 described by Rempen 11 in two of 150 pregnant women (1.3%) scanned between 8 and 12 weeks gestation. In both cases a single cyst was detected at 9 weeks gestation; one, measuring 6 mm, was identified within the amniotic cavity, but the other, measuring 11 mm, was extraamniotic in location and clearly different from the yolk sac. These cysts were no longer present at the second trimester follow-up scan, and both infants were normal at birth. Subsequently, Skibo and coworkers 12 found first trimester umbilical cord cysts in eight of 2070 pregnancies (0.4%) in which scanning was performed between 8 and 12 weeks gestation. In all of their cases the cyst was detected between 8 and 9 weeks, measured from 2 to 7 mm, and resolved spontaneously by 12 weeks. Normal pregnancy outcome was documented in all five cases followed to term. A higher prevalence of 3.4% (29 cases in 859 pregnancies) was reported in a screening study of umbilical cord cysts at 7 to 13 weeks gestation. 13 In about 75% of these cases the cyst was detected between 8 and 9 weeks, and 85% of them resolved by 12 weeks. The origin of first trimester umbilical cord cysts is still unknown. Current theories suggest that they probably represent embryonic remnants such as allantoic or omphalomesenteric cysts, amniotic inclusion cyst, or mucoid degeneration or edema of the Wharton jelly (pseudocysts). In the only case in which sonographic-histopathologic correlation is available, 12 an amniotic inclusion cyst and adjacent mucoid degeneration of the Wharton jelly were found, suggesting that first trimester umbilical cord cysts could represent either entity. Ross and colleagues, 13 on the basis of the rapid resolution of the cysts, suggested that they represent pseudocysts rather than true cysts. These investigators also noted that the formation of cysts is coincidental with both the onset of umbilical cord coiling and the formation of the physiologic midgut hernia; they hypothesized that these developmental phenomena could increase hydrostatic pressure within the umbilical vessels, favoring exudation of water into the Wharton jelly and formation of pseudocysts. This mechanism may be similar to the one suggested for formation of pseudocysts in second and third trimester fetuses with growth restriction, omphalocele, and chromosomal disorders. 10 The prognostic significance of first trimester umbilical cord cysts remains controversial. Our series, although small, showed no association with adverse pregnancy outcome; none of the cases was associated with pregnancy loss, and none of the fetuses had associated structural anomalies. These findings are in keeping with two previous reports, 11,12 although they were in contrast to a recent series reporting that seven of 27 fetuses (26%) with first trimester umbilical cord cysts had structural or chromosomal defects, including two cases of trisomy 18 and one case each of arthrogryposis, obstructive uropathy, cystic hygroma, anencephaly, and omphalocele. 13 Noteworthy, the investigators identified several poor prognostic signs for fetal anomalies, including paraxial location of the cyst, location of the cyst closer to the fetal or placental insertion but not in the middle of the cord, and persistence of the cyst beyond 12 weeks gestation. In our series, the cysts were noted to be eccentrically positioned with respect to the umbilical cord axis and to be located in the middle segment of the cord in the vast majority of cases. Doppler sonographic studies of the umbil- Figure 2 Bidimensional (A) and color Doppler imaging (B) of umbilical cord cyst (small arrow) at 8 weeks 2 days shows the close connection of the cyst with the umbilical cord and absence of blood flow within the cyst. Open arrow denotes the yolk sac. A B

4 98 FIRST TRIMESTER UMBILICAL CORD CYSTS J Ultrasound Med 18:95 99, 1999 Table 1: First Trimester Umbilical Cord Cyst Case MA (yr) Indication for Scan GA CRL (mm) Cyst Diameter (mm) Pregnancy Outcome 1 35 Dating 9 wk 3 da 25 6 Normal 2 17 Dating 9 wk 1 da 23 6 Normal 3 32 Dating 9 wk 0 da 24 6 Normal 4 26 Dating 8 wk 4 da 23 5 Normal 5 24 Dating 8 wk 4 da 20 5 Normal 6 23 Dating 8 wk 6 da 21 4 Lost to follow-up 7 23 Dating 8 wk 2 da 19 4 Normal 8 24 Dating 8 wk 1 da 18 4 Normal 9 38 Dating 8 wk 3 da 15 3 Normal Dating 8 wk 2 da 17 3 Normal MA, Maternal age; GA, gestational age; CRL, crown-rump length. ical cord demonstrated no deleterious effect of the cyst on umbilical artery and vein blood flow velocity waveforms. Furthermore, no evidence of umbilical cord cysts was found during the second trimester, confirming that early resolution is a good prognostic sign. Indeed, one series reported that persistence of the cysts beyond 12 weeks gestation was invariably associated with fetal structural defects. 13 Discrepancies in pregnancy outcome between our series and the one presented by Ross and coworkers 13 could be explained by the fact that the majority of cases in Ross and colleagues study came from a high-risk population, whereas our cases were detected mainly in low-risk pregnancies, in which an early first trimester scan usually is performed routinely for pregnancy dating. Further screening studies in both low-risk and high-risk populations are needed to clarify this issue. In summary, our study shows that the incidental detection of an umbilical cord cyst in the first trimester is not associated with adverse pregnancy outcome in low-risk pregnancies. However, a followup scan is important to identify those occasional pregnancies in which the cyst persists and might be associated with fetal chromosomal and structural defects. The significance of first trimester umbilical cord cysts in a high-risk population remains to be elucidated. Figure 3 Umbilical cord cyst (small arrow) at 9 weeks and 1 day (A) with pulsed Doppler assessment of the umbilical cord (B) shows normal blood flow velocity waveforms characterized by absent end diastolic flow in the umbilical artery and pulsations in the umbilical vein. Open arrow denotes the yolk sac. A B

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