Fertilization of human oocytes in relation to varying delay before insemination

Fertilization and pregnancy rates in an in vitro fertilization and embryo transfer program were studied after a range of insemination times of between 1 and 26 hours after oocyte recovery. There was no significant variation in fertilization rate across this range. The pregnancy rate showed no significant variation for insemination between 3 and 16 hours after aspiration. However, it was disappointing at 2 hours (3%), and no pregnancies were achieved from the nine patients whose ova were inseminated 20 or more hours after aspiration. It is concluded that mature oocytes can be inseminated in vitro at any time between 3 and 16 hours after aspiration and still retain the same potential to produce a pregnancy.