ABSTRACT BACKGROUND: It is very common to offer low molecular weight heparin (LMWH) medications to women with unexplained habitual abortion, to increase the livebirth rate. Although no benefit from LMWH has been clearly demonstrated, examination of the effects of enoxaparin on placental structure is lacking. OBJECTIVE: To assess placental structural changes in pregnancies treated with enoxaparin, compared with controls. DESIGN AND SETTING: Case-control study in an obstetrics and gynecology unit of a tertiary-level university hospital in Turkey. METHODS: Forty patients who had had term pregnancies and live births but also histories of habitual abortion were recruited for this study. Placentas were sampled using a systematic random sampling method. Tissue samples were obtained, embedded and sectioned for routine histological analyses. Hematoxylin and eosin staining was used. Surface area and length estimates from placental components were evaluated by using Image J. Cell proliferation and apoptosis were also assessed via immunohistochemistry. RESULTS: There were no significant differences between the groups regarding maternal age, abortion rate, birth weight or gestational age. Comparison of the enoxaparin and control groups showed that there were no significant differences in terms of surface area and ratios of placental components. We found that Bcl-2 was generally expressed at high levels in the enoxaparin group, while there was no difference in terms of Ki-67 between the groups. CONCLUSIONS: This study demonstrates that enoxaparin did not show any significant effect on the placental structure of cases that had histories of habitual abortion.