Use of low-molecular-weight heparin from the first trimester of pregnancy: a retrospective study of 111 consecutive pregnancies.

Abstract Background During the first trimester of pregnancy, unfractionated heparin is the standard anticoagulant treatment for pregnant women at high risk of thrombosis. Objective To observe maternal and fetal tolerance for low-molecular-weight heparin begun in the first trimester of pregnancy. Methods Observational study conducted from 1 January 1997 to 31 May 2001. All patients began treatment before the 15th week of pregnancy. The outcome measures were the incidence and causality of adverse events in mother and fetus. Results The study included 97 patients (and 111 pregnancies) at very high risk for thrombosis. Seven fetal losses (6.3%) were observed: three early spontaneous abortions, three late spontaneous abortions and one medically indicated abortion. Twenty-five (22.5%) bleeding events occurred during pregnancy, seven (6.3%) of which required medical intervention: five curettages for first trimester spontaneous abortions, one late abortion at 21 weeks and one placental abruption at 25 weeks. Of nine (8.1%) primary postpartum hemorrhages involving a blood loss ≥500 mL, three involved losses of 1000 mL or more and one required embolization of the uterine arteries. Five patients had thrombocytopenia, but none was treatment-related. Local cutaneous reactions occurred in 33 (29.7%) patients. Six (5.4%) maternal thromboembolic complications occurred during pregnancy or postpartum. At birth, two children had non-chromosomal congenital malformations (pyelectasia, cleft lip and palate). No fetal or neonatal complication was attributed to the treatment. Conclusion The use of low-molecular-weight heparin (LMWH) for patients requiring anticoagulant treatment from the first trimester appears safe for mother and fetus.