Comparative incidence of pregnancy outcomes in thrombophilia-positive women from the NOH-APS observational study.

The incidence of pregnancy outcomes in women with constitutive thrombophilia is uncertain. We observed women with no history of thrombotic events (nonthrombotic), who had experienced 3 consecutive spontaneous abortions before the 10th week of gestation or 1 fetal death at or beyond the 10th week of gestation. We compared the frequencies of complications during a new pregnancy attempt among women carrying the F5 rs6025 or F2 rs1799963 polymorphism (n = 279; low-molecular-weight heparin [LMWH] treatment during pregnancy only in case of prior fetal death), and women with negative thrombophilia screening results as control women (n = 796; no treatment). Among women with prior recurrent abortions, thrombophilic women were at increased risk for fetal death. Among women with prior fetal death, thrombophilic women experienced less fetal death recurrences, less preterm births and preeclampsia, and more live births as they were treated with LMWH. In nonthrombotic F5 rs6025 or F2 rs1799963 heterozygous women with prior pregnancy loss, fetal loss may indicate a clinical subgroup in which future therapeutic randomized controlled trials testing the effect of LMWH prophylaxis are required in priority.