Background: The factor V Leiden (FVL) and prothrombin 20210A (PTm) mutations are associated with single late pregnancy loss and recurrent early pregnancy loss. The prognosis after an initial loss in women with thrombophilia is uncertain.
Objective: To assess the pregnancy outcome of the second pregnancy after a first loss in women with and without either FVL or PTm mutations.
Methods: We selected women with a first pregnancy loss out of two family cohorts of first degree relatives of probands with FVL or PTm mutations and a history of documented venous thromboembolism or premature atherosclerosis.
Results: Ninety-three women had had a first pregnancy loss and became pregnant a second time. Their risk of loss of the subsequent pregnancy was higher than in 825 women with a successful first pregnancy [25 vs. 12%, relative risk (RR) 2.0, 95% CI 1.4-3.0]. The live birth rate of the second pregnancy after an early first loss (<or= 12 weeks of gestation) was 77% (95% CI 62-87) for carriers and 76% (95% CI 57-89) for non-carriers (RR 1.0, 95% CI 0.8-1.3). After a late first loss (> 12 weeks), the live birth rates were 68% (95% CI 46-85) and 80% (95% CI 49-94) for carriers and non-carriers, respectively (RR 0.9, 95% CI 0.5-1.3).
Conclusions: Women with a first pregnancy loss have a 2-fold increased risk of loss of the subsequent pregnancy, regardless of their carrier status. More importantly, the outcome of the second pregnancy is rather favorable in absolute terms, even for those with thrombophilia and a late loss, which raises concern regarding the risks and presumed benefits of anticoagulant therapy in these women.