Treatment-independent pregnancy among infertile couples.

We analyzed a two- to seven-year follow-up of 1145 infertile couples to determine the frequency of pregnancy occurring independently of treatment. Pregnancy occurred in 246 of 597 treated couples (41 per cent) and in 191 of 548 untreated couples (35 per cent). Thirty-one per cent of the pregnancies in treated couples occurred more than 3 months after the last medical treatment or more than 12 months after adnexal surgery. These pregnancies plus the 191 pregnancies in untreated couples constituted the category of "treatment-independent pregnancies" and accounted for 61 per cent of all pregnancies; for 44 per cent of those among couples with ovulation deficiency; for 61 per cent of those in couples with endometriosis, tubal defects, or seminal deficiencies; and for 96 per cent of those in couples with cervical factors or idiopathic infertility. We conclude that the potential for a spontaneous cure of infertility is high, that treatment for many classes of infertility should be evaluated by randomized clinical trials, and that in such trials random assignment of subjects to untreated control groups would be ethically acceptable.