Clinical factors affecting pregnancy rates among infertile couples.

In a follow-up study of 1297 couples registered at a Nova Scotia infertility clinic with a complaint of infertility of at least 12 months' duration, the cumulative pregnancy rate at 36 months, with 95% confidence limits, was found to be 49 +/- 4%. The predictors of pregnancy by univariate analysis were a favourable primary clinical diagnosis (p less than 0.001), a duration of infertility of less than 3 years (p less than 0.001), a single diagnosis for the infertility (p less than 0.001), a previous pregnancy in the partnership (p = 0.001) and a length of marriage of less than 4 years (p = 0.002). Proportional hazards analysis confirmed these variables as predictors of pregnancy. The highest cumulative pregnancy rates after 12 and 36 months of follow-up were observed in cases of ovulation deficiency, and the lowest were seen in cases of tubal defects. However, before the process of diagnosing infertility begins, useful prognostic information can be determined from the length of marriage, the duration of infertility and the partnership's history of previous pregnancy.