The Fetal Safety of Enoxaparin Use During Pregnancy: A Population-Based Retrospective Cohort Study

Introduction: Enoxaparin is widely used during pregnancy as pregnancy is a hypercoagulable state; however, its fetal safety has scarcely been investigated. Objective: Our study aimed to examine fetal safety following enoxaparin exposure during pregnancy. Methods: A population-based, retrospective cohort study was performed by linking computerized databases, including the drug dispensing registries of Clalit Health Services in Israel and maternal and infant hospital records, between 1998 and 2009. Multivariate logistic regression models were used to examine associations between first- and third-trimester exposure to enoxaparin, major malformations, and other adverse birth outcomes, adjusted for confounders. Results: From a total of 109,473 singleton pregnancies, 418 and 572 were exposed to enoxaparin during the first and third trimesters, respectively. Exposure to enoxaparin during the first trimester of pregnancy was not associated with an increased risk of major congenital malformations [adjusted odds ratio (aOR) 1.1, 95% confidence interval (CI) 0.8–1.6], while exposure during the third trimester was not associated with an increased risk of low birth weight (aOR 1.1, 95% CI 0.8–1.4), low Apgar score (aOR 0.9, 95% CI 0.4–1.8), or risk of perinatal mortality (aOR 0.6, 95% CI 0.1–2.9). Conclusion: Exposure to enoxaparin during pregnancy was not associated with an increased risk of major malformations in general or according to organ systems. Nonetheless, risk for specific malformations cannot be ruled out.