Diagnosing umbilical cord entanglement in monoamniotic twins: becoming easier and probably essential...

Abstract

A 33-year-old primigravid woman was diagnosed with a monoamniotic pregnancy at 13 weeks' gestation. Two-dimensional (2D) ultrasound examination at 16 weeks showed that all umbilical vessels between the two fetuses could be mobilized simultaneously by pressing the abdomen and Doppler examination recorded two different heart rates within a vascular mass which was diagnosed as cord entanglement. At 26 weeks, the woman was hospitalized for intensive surveillance, with non-stress tests being performed two to three times daily. At 29 weeks, the entanglement was clearly visible with power Doppler on both color (Figure 1a) and three-dimensional (3D) volume-rendered (Figure 1b) images of the vessels. Ultrasound examinations were performed using a Voluson 730 (Kretztechnik AG, Zipf, Austria) ultrasound machine. All non-stress tests and sonographic examinations were normal for both twins. A Cesarean section was performed at 35 weeks, several days after intramuscular corticosteroid injection to enhance lung maturation. Both twins, which were girls, were liveborn. They had Apgar scores of 10 at 1 and 5 min and birth weights of 2300 g and 2500 g. The entanglement, which closely resembled the prenatal 3D image, was visible during the Cesarean section (Figure 2). The neonatal period was uneventful, and the girls were discharged from hospital with their mother on day 8. The pathologist confirmed the diagnosis of multiple cord entanglement without tight knots. The cords were entangled at a distance of 21 cm from the chorion. Two-dimensional power Doppler ultrasound image (a) and three-dimensional power Doppler volume-rendered image (b) demonstrating multiple loops of entangled umbilical cord at 29 weeks. Photograph showing the cord entanglement during Cesarean section at 35 weeks. Perinatal mortality in monoamniotic twins is very high, reported rates ranging between 28% and 47%1. Cord entanglement is the leading cause of death in this rare twin population and may be responsible for half of all deaths in this population1. Today's literature includes descriptions of several sonographic signs that make possible its diagnosis. Although the diagnosis can be made with 2D Doppler, 3D images provide clearer visualization of the tangled vessels and can help illustrate the problem to the parents. Intensive antenatal surveillance following the diagnosis of entanglement has recently been suggested to improve survival rates2, 3. Roqué et al. reviewed the literature and reported that in the 133 non-anomalous monoamniotic pregnancies reported between 1990 and 2002, the perinatal mortality rate was 7.0% (4/60) among those with an antenatal diagnosis, compared with 21.6% (38/176) for those not diagnosed antenatally2. This difference may be due to retrospective bias or to intensive surveillance of antenatally diagnosed monoamniotic pregnancies. The younger gestational age at delivery of the pregnancies diagnosed antenatally in this series supports the latter argument. Likewise, Rodis et al., in a 10-year series of 13 pregnancies, reported a very impressive survival rate of 92% (24/26)3. In all these cases, intensive surveillance, usually followed by daily non-stress tests beginning at 24–26 weeks, was performed. Cord entanglement was observed at birth for all 13 sets of monoamniotic twins in their study; in eight cases, ominous fetal heart traces indicated the need for delivery. Many different 2D sonographic signs can confirm or rule out cord entanglement1 and 3D volume-rendered images can provide additional details. While a formal study of the diagnostic value of each sign is not feasible, today we can be almost certain about the presence of cord entanglement. Like other authors2, 3, we consider that the possibility of fetal death associated with the diagnosis might encourage obstetricians who diagnose cord entanglement to propose intensive surveillance during the third trimester, with daily non-stress tests. Nonetheless these recommendations cannot prevent all such deaths. C. Vayssière*, C. Plumeré*, B. Gasser*, M. Neumann*, R. Favre*, I. Nisand*, * Department of Obstetrics Gynaecology, University Louis Pasteur, SIHCUS-CMCO, Strasbourg, France