Key Points• Among women with pure obstetric APS, late pregnancy complications are more frequent in cases of prior fetal loss.• Late pregnancy complications are more frequent among women treated for pure obstetric APS than among nontreated controls.The incidence of pregnancy outcomes for women with the purely obstetric form of antiphospholipid syndrome (APS) treated with prophylactic low-molecular-weight heparin (LMWH) plus low-dose aspirin (LDA) has not been documented. We observed women without a history of thrombosis who had experienced 3 consecutive spontaneous abortions before the 10th week of gestation or 1 fetal loss at or beyond the 10th week.We compared the frequencies of complications during new pregnancies between treated women with APS (n 5 513; LMWH 1 LDA) and women negative for antiphospholipid antibodies as controls (n 5 791; no treatment). Among APS women, prior fetal loss was a risk factor for fetal loss, preeclampsia (PE), premature birth, and the occurrence of any placenta-mediated complication. Being positive for anticardiolipin immunoglobulin M antibodies was a risk factor for any placenta-mediated complication. Among women with a history of recurrent abortion, APS women were at a higher risk than other women of PE, placenta-mediated complications, and neonatal mortality. Among women with prior fetal loss, LMWH 1 LDA-treated APS women had lower pregnancy loss rates but higher PE rates than other women. Improved therapies, in particular better prophylaxis of late pregnancy complications, are urgently needed for obstetric APS and should be evaluated according to the type of pregnancy loss. (Blood. 2014;123(3):404-413)

The incidence of thrombosis in the purely obstetric form of antiphospholipid syndrome is uncertain. We performed a 10-year observational study of 1592 nonthrombotic women 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 thrombotic events among women positive for antiphospholipid Abs (n ‫؍‬ 517), women carrying the F5 6025 or

Key Points• Fetal death is more frequent in women with prior abortions carrying F5 rs6025 or F2 rs1799963 polymorphisms vs nonthrombophilic women.• Pregnancy complications are less frequent in LMWH-treated thrombophilic women with fetal loss vs untreated nonthrombophilic women.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 5 279; 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 5 796; 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. (Blood. 2014;123(3):414-421)