
Abstract
Objective Low-molecular-weight heparin (LMWH) is used during pregnancy in
women diagnosed with thrombophilia for prevention of thromboembolic events and
prevention of recurrent pregnancy loss. Prophylactic dosing does not always
achieve target anti-FXa levels of 0.2–0.6 IU/ml. We
aimed to determine if anti-FXa levels, measured in the first trimester, have an
influence on pregnancy outcome.
Material and Methods Eighty-one first-trimester women with a history of
adverse pregnancy outcomes under LMWH therapy during pregnancy were enrolled in
this study. Anti-FXa levels were measured in the first trimester, and fetal and
maternal outcomes were recorded.
Results The mean age of women was 28±4 (19–40) and mean
anti-FXa level 0.44±0.93 IU/ml. No bleeding or clotting
complications were associated with LMWH administration. Anti-FXa levels did not
have a relationship with gestational age at birth, fetal weight, type of
delivery, cesarean indications, postpartum bleeding, APGAR scores, or admission
to the neonatal intensive care unit (p>0.005). Anti-FXa levels were not
correlated with live birth rates.
Conclusion Anti-FXa levels did not have an influence on pregnancy and
fetal outcomes. The effect of LMWH on pregnancy outcomes may not be due to
anticoagulant activity but other mechanisms.
Keywords
Anti-FXa level - low molecular weight heparin - recurrent pregnancy loss - pregnancy