An obstetric analysis of fifty consecutive pregnancies after transfer of cryopreserved human embryos.

This report describes the obstetric outcome in 50 pregnancies resulting from the transfer of human embryos that had been cryopreserved for up to 2 years. The duration of cryopreservation did not influence the pregnancy rate after thawed embryo transfer. Thirty-one babies have been born from 28 pregnancies and a further seven pregnancies are currently in the second and third trimesters. Twenty-eight percent of the pregnancies failed to progress beyond the first trimester. One pregnancy was terminated at 22 weeks' gestation because of severe fetal malformation. Important antenatal events included premature uterine activity in six patients although only one patient with a singleton pregnancy ultimately was delivered prematurely. Retroplacental hemorrhage occurred in four patients but was of clinical consequence in only one. There was a high incidence of breech presentation at term in singleton pregnancies (12%). The cesarean section rate in this series was 21%. An international registry of cryopreserved pregnancies would facilitate data collection in this relatively new clinical field.