Clinical implications of developments in in vitro fertilisation.

During February 1979 to December 1983, 831 infertile couples were treated by in vitro fertilisation and embryo transfer. The problems they faced included deciding on the number of oocytes to be collected at laparoscopy, the numbers to be donated or fertilised, the numbers of embryos to be transferred and frozen, and whether abnormal embryos should be used for research or discarded. The 831 patients received a total of 1530 treatment cycles. Of the 763 patients for whom complete data were available, 136 (17.8%) became pregnant. The rate of pregnancy, however, increased dramatically from 7.4% when only one embryo was transferred to 21.1% and 28.1% when two and three embryos were transferred, respectively. The chance of multiple pregnancy also increased with the number of embryos transferred, but the risk (2% for twins) was far outweighed by the relatively poor result after transferring a single embryo. Out of 40 embryos freeze-thawed, 23 survived thawing and were transferred; of these, 4 (17%) resulted in pregnancy. Thirty four transfers of donor oocyte embryos also resulted in four pregnancies (12%), but two of these ended in abortion. Neither microscopy nor any other available test can determine the potential of an oocyte to result in pregnancy, so that discarding oocytes that may look abnormal simply reduces the chances of conception--both for the patient and for any prospective recipient of donor oocyte embryos. In any case, abnormal embryos tend to die when growth is allowed to continue in vitro. Probably all oocytes harvested from a patient should be inseminated and the utilisation of the embryos decided once the number developed is known.