Human in-vitro fertilisation, in-vivo sperm penetration of cervical mucus, and unexplained infertility.

Oocytes were recovered at routine diagnostic laparoscopy for infertility after stimulation with clomiphene and human chorionic gonadotropin. The results of in-vitro fertilisation (IVF) with the husband's semen were compared in 3 distinct groups of fully investigated infertile couples. Those with bilateral tubal occlusion (36) were combined with fertile controls undergoing sterilisation (6) to form a "tubal" group for normal reference. In this tubal group 48/88 (55%) oocytes were fertilised, at least one oocyte being fertilised in each of 33/42 couples (79%). In couples with a negative or poor postcoital test (PCT), despite mostly normal semen analysis, 8/50 (16%) oocytes were fertilised in 6/21 (29%) couples. In couples with unexplained infertility and a positive PCT, 22/61 (36%) oocytes were fertilised in 17/25 (68%) couples. The results show that spermatozoa unable to penetrate preovulatory cervical mucus are generally also unable to fertilise the human oocyte. They emphasise the biological and prognostic importance of the PCT, and the hidden frequency of defective sperm function as a cause of unexplained infertility. Human IVF is likely to be a more helpful diagnostic investigation than hamster egg penetration testing because it is specific for individual couples. If IVF is to offer therapeutic hope to couples with impaired sperm/mucus penetration the fertilisation rates and the numbers of mature oocytes stimulated for recovery will both have to be high.