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Umbilical cord entanglement in monoamniotic twins

2012; Wiley; Volume: 40; Issue: 1 Linguagem: Inglês

10.1002/uog.11129

1469-0705

U. Zöllner, M Rehn, Stefan Heuer, Ann-Katrin Morr, J. Dietl,

Pregnancy and preeclampsia studies

Monoamniotic twins are very rare, occurring with a frequency of 0.004% of all live births1. When a human embryo, at blastocyst stage, divides as late as the 8th day following fertilization, the result is monochorionic monoamniotic twins, which constitute approximately only 1% of all monozygotic twins2. Due to the numerous possible complications associated with monoamniocity, early delivery at 32 weeks' gestation by primary Cesarean section is recommended1. The perinatal mortality rate is 28–60%. We report clinical and imaging findings in a 27-year-old primigravida, who came to our clinic for the first time at 22 + 4 weeks of pregnancy. In the first trimester, the referring gynecologist had diagnosed monoamniotic twin pregnancy. There were no other pregnancy-associated complications. Weekly ultrasound follow-up examinations showed appropriate growth of both fetuses and absence of signs of twin-to-twin transfusion syndrome. No fetal anomalies were diagnosed. Umbilical artery and fetal middle cerebral artery blood flow measurements were normal in both cases. The umbilical cord had a ball-of-wool-like configuration (Figure 1a). On color Doppler sonography there were no signs of a knot or constriction (Figure 1). To optimize monitoring, the patient was admitted at the 30th week of gestation. Cardiotocography was performed daily and showed no abnormal results. In order to avoid possible complications associated with cord entanglement, a primary Cesarean section was performed at 32 + 5 weeks. Umbilical cord entanglement on two-dimensional (a) and three-dimensional (b) color Doppler imaging in monoamniotic twins at 28 weeks' gestation. Delivery of the first twin showed it to be normally developed and the umbilical cord was cut without complication (Apgar scores, 7, 8 and 9 at 1, 5 and 10 min, respectively; arterial pH, 7.36; weight, 1920 g). The second twin (Apgar scores, 8, 9 and 9; arterial pH, 7.36, weight, 1470 g) had multiple coils of umbilical cord wrapped around the neck (Figure 2a). The umbilical cord convolution involved the cords of both twins (Figure 2b). The neonatal period and pediatric follow-up were problem-free. On delivery at 32 + 5 weeks, the second twin showed umbilical cord wrapped around the neck (a) and, on removal of the cord and placenta, entanglement was seen to involve the cords of both twins (b). Due to the lack of prospective randomized studies, there is no consensus regarding the monitoring of monoamniotic twin pregnancies or the timing and mode of their delivery, though early Cesarean section is generally recommended1. It is likely that umbilical cord constrictions are common in monoamniotic twins but that the high perinatal mortality represents a consequence of other anomalies, such as twin reversed arterial perfusion sequence3, 4.