[Freezing, thawing and transfer of human embryos]

We present our experience of cryopreservation of human embryos from 1 July 1987 to 1 July 1989. During this period, 667 in vitro fertilizing cycles were completed. In 173 (26%) of these cycles, a total of 805 surplus embryos were cryopreserved. 516 embryos were thawed and 247 of these were transferred to the uterine cavity in a total of 110 replacement cycles. This resulted in 22 (20%) pregnancies in which a total of 28 gestational sacs could be verified by ultrasound. Seven of the pregnancies aborted spontaneously in the first trimester and one pregnancy was ectopic. By 1 July 1989, five singleton pregnancies were in progress and 13 babies had been born from nine deliveries (one set of triplets and two sets of twins). 25% of the patients whose embryos were cryopreserved became pregnant in the in vitro fertilizing cycle after replacement of fresh embryos.