- 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.