Time-to-Pregnancy in Women with Unexplained Recurrent Pregnancy Loss: A Controlled Study

To determine whether differences are present in the time-to-pregnancy (TTP) between women with unexplained recurrent pregnancy loss (uRPL) and control women, in this case-control, retrospective study, carried out in tertiary university hospitals, the TTP, defined as the months needed to reach pregnancy from when the woman started to try to conceive, was determined in 512 women, 207 of which were diagnosed as having uRPL and 305 were normal healthy control women. The specific TTPs for each pregnancy, stratified by order of pregnancy occurrence, were also determined. Pregnancy rates by time were calculated by using the Kaplan-Meier method to construct the survival curves. The age at which the pregnancies occurred was determined. Comparisons were carried out between women with uRPL and controls. Overall, 1192 pregnancies occurred and were analyzed. Mean TTP in uRPL women was shorter than in controls (P < 0.001) when all the pregnancies were considered. Similarly, it was shorter in the first, second, third, and fifth pregnancy. The pregnancy rates of uRPL women were shorter than that of control women for the first three pregnancies, for which the numbers of subjects allowed the comparisons to be made. These findings were observed despite maternal age of uRPL women was higher than that of control women. TTP is shorter in uRPL than in normal women. This finding clinically supports to the hypothesis that women with uRPL could be, at least in early stages of pregnancy, more fertile or receptive toward the implanting embryo than healthy women.