Long-term follow-up of the apparently normal couple with a complaint of infertility.

Ninety-one couples with no obvious cause for their infertility were followed after periods of 1 to 17 years (96% were followed until they conceived or for more than 5 years). All of the couples had been fully investigated and no specific abnormality had been demonstrated. The majority of women (88%) had primary infertility of at least 2 years' duration, although a small number (12%) had had one or more first-trimester abortions and were thus classified as having secondary infertility. Cumulative conception rates (using life tables) at the end of 7 years were 36.2% for the primary infertility group and 78.8% for the women with secondary infertility. Of those couples achieving a first pregnancy and desiring a second, only 44.3% had conceived at the end of another 4-year period. These rates are markedly lower than the published conception rates of a normal population.