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Fertilization rate in couples with unexplained infertility.

A group of 24 couples with unexplained infertility was scheduled for in-vitro fertilization and tubal embryo transfer between May 1989 and September 1990. In the same period, in-vitro fertilization and intrauterine transfer of embryos was planned in a control group of 44 women with tubal infertility. The mean age and duration of infertility were similar in both groups and the same scheme of ovarian stimulation was used. No statistically significant difference was obtained comparing oestradiol levels and numbers of mature oocytes retrieved between the group of patients with unexplained infertility and those with tubal infertility. The fertilization rate of the oocytes obtained from women with unexplained infertility (60.4%) was significantly lower (P less than 0.001) than that of the oocytes obtained from patients with tubal infertility (87.3%). There was no statistically significant difference in the cleavage rates between patients with unexplained infertility and those with tubal infertility. It is concluded that lack of fertilization is an unexplored cause of infertility in couples with unexplained infertility.