The effect of treatment on pregnancy among couples with unexplained infertility.

Our objective was to determine the effect of treatment on the likelihood of pregnancy among couples with unexplained infertility. We used a nonrandomized, prospective, multicentered cohort analytic study, with mean follow-up time of 14.5 months (range, 0.5-46 months). The subjects were 470 couples who attended infertility clinics affiliated with medical schools in Canada, in whom no abnormality was found after investigation. They were drawn from a total of 2,106 couples registered from April 1, 1984 to March 31, 1987. Of these, 130 couples were selected for treatment at the discretion of the care givers; 340 couples were not treated. Selection for treatment resulted in imbalance between the groups: the treated couples had a longer mean duration of infertility (48 vs. 36 months), and were more likely to have had a laparoscopy as part of the investigation (72% vs. 48%). No specific protocol of treatment was used. Treatments most commonly used were clomiphene (87); gonadotropins (31); intrauterine insemination (20); IVF or GIFT (16); bromocriptine (12); 43 couples had two treatments, and 11 had three treatments. The only important determinants of treatment (logistic regression) were time under observation and laparoscopy status. Duration of infertility was only a minor determinant of treatment. Crude, unadjusted pregnancy rates were 25% for the treated group and 34% for the untreated group. The early occurrence of pregnancy in the untreated couples accounted for much of this difference. After adjustment for baseline differences between the groups and times to and under treatment with proportional hazards analysis, the cumulative probability of pregnancy is 2.0 (95% CI 1.3 to 3.1) times as high with treatment.(ABSTRACT TRUNCATED AT 250 WORDS)