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Umbilical cord entanglement in monoamniotic twins

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 27year-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-totwin 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. 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. Due to the lack of prospective randomized studies, there is no consensus regarding the monitoring of Figure 1 Umbilical cord entanglement on two-dimensional (a) and three-dimensional (b) color Doppler imaging in monoamniotic twins at 28 weeks’ gestation.