Summary

Perinatal morbidity and mortality rates for vasa previa are high when it is not diagnosed antenatally. In this report, a case of vasa previa in a twin pregnancy was diagnosed postnatally, which leads to complications with the first twin. Serial ultrasound during pregnancy did not diagnose a bilobed placenta, a velamentous insertion of the umbilical cord or vasa previa. At 37 weeks, vaginal bleeding was detected in the expulsive stage and vaginal-assisted delivery of both fetuses was undertaken. The first fetus was born pale and anaemic, and required a blood transfusion and therapeutic hypothermia. A high risk of vasa previa is associated with placentas with low-lying insertion, bilobed placentas, velamentous insertions of the umbilical cord, multiple pregnancy and pregnancies conceived after the use of assisted reproductive technologies. Transvaginal ultrasound screening with colour flow Doppler can allow antenatal diagnoses of vasa previa and an improved outcome.