A proportional hazards analysis of the clinical characteristics of infertile couples.

Evaluated were methods of ordering the many possible predictors of infertility outcome. The clinical characteristics of infertile couples were studied with respect to the occurrence of pregnancy during follow-up, by means of the methods of survival analysis. Among 1,297 couples who were infertile for 12 months or more, the cumulative pregnancy rate at 36 months with 95% confidence limits was 49% +/- 4%. The proportional hazards analysis identified three independent predictors of the occurrence of pregnancy from the couple's history (with P values in brackets): a history of pregnancy in the partnership (0.0001); shorter duration of infertility (0.0001); and shorter length of marriage (0.005). The predictors arising from the diagnostic process (with P values in brackets) were: fewer infertility diagnoses (0.0001); a favorable primary clinical diagnosis (0.001); and the presence of any tubal disease, regardless of the primary clinical diagnosis (0.001). The analysis selected an economical set of significant predictor variables and demonstrated that a longer period of contraception was associated with a lower pregnancy rate among infertile couples. Also, three simple questions from the history were nearly equivalent to the entire diagnostic process as predictors of the outcome.