[Single intrauterine fetal death in twin pregnancy]

During a 11 year period (1984-1994) we identified and analysed at the Department of Obstetrics, University Hospital of Zurich, among 541 twin pregnancies 19 with single intrauterine death (SIUD) in the second and third trimester. The preterm delivery rate was 68% and much higher compared to singleton pregnancies at the same institution (17%). The caesarean section rate was 47% and also higher compared to singleton pregnancies (21%) but lower than in a normal twin collective (61%). Two of the surviving twins showed malformations. One of them has in addition of porencephaly, probably due to disruption syndrome. In 12 out of 19 case a monochorionic placenta was found including 5 with twin-twin transfusion syndrome. Surprisingly 8 out of 19 dead fetuses had a velamentous insertion of the umbilical cord. This might suggest a causal relationship to SIUD. 95% showed the same sex. Maternal blood coagulation disorders are rare. From our results we conclude that SIUD is associated with an increased preterm delivery and caesarean section rate. Monochorionic twins and twins with concordant sex demonstrate the highest risk for SIUD. The twin-twin transfusion syndrome is the main single cause for SIUD. The pathophysiologic role of velamentous insertion remains unclear.