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There are several possible mechanisms by which antiphospholipid antibodies (aPL) may have adverse effects on placental functions. Examination of placentas and first-trimester decidua from antiphospholipid syndrome-complicated pregnancies has found little evidence of specific thrombotic placental pathology. It is now generally accepted that the clinically relevant aPL bind to proteins with affinity for phospholipids. The most important epitope for antiphospholipid syndrome-related aPL resides on beta2-glycoprotein-I (beta2GPI). aPL detected by anti-beta2GPI assays are associated with fetal loss. During differentiation to syncytium, trophoblasts express cell membrane anionic phospholipids that can bind beta2GPI. Adhered beta2GPI can be recognized by the antibodies that, once bound, interfere with trophoblast cell maturation, resulting in defective placentation. The improved outcome of pregnancies treated with heparin stimulated interest on the drug's mechanism of action. Several mechanisms could explain its beneficial effects in addition to a direct effect of heparin on the coagulation cascade. It might reduce the binding of aPL, inflammation by inhibiting complement activation, and might facilitate implantation. Further investigations are needed to better understand how aPL induce obstetric complications and to better clarify the functional role of heparin in the human placenta, leading to more successful therapeutic options.

Objective: To verify whether prophylaxis with low-molecular-weight heparin (LMWH) and low-dose aspirin (LDA) could positively affect pregnancy outcome in women with a history of severe preeclampsia., Methods: We compared 23 pregnancies treated with LDA alone to 31 pregnancies treated with LMWH plus LDA., Results: Women treated with LMWH-LDA (n = 31) showed a better pregnancy outcome than those treated with LDA alone (n = 23) in terms of gestational age at delivery (p < 0.05), birth weight (p < 0.01), birth weight percentile (p < 0.01), and rate of preeclampsia (p < 0.01). Furthermore, comparing the intra-group outcome variation between previous and index pregnancies, an improvement appeared in each group, but a more pronounced gain was noted in the LMWH-LDA group in terms of gestational age at delivery (p< 0.005), birth weight (p < 0.005), and birth weight percentile (p < 0.005)., Conclusions: Thromboprophylaxis with LMWH plus LDA can improve pregnancy outcome in women with previous severe preeclampsia.