For all women included in the study, blood samples will be tested for anticardiolipin antibodies and lupus anticoagulant. The clinical details of all women will be collected by reviewing their hospital and prenatal records. The following clinical characteristics will be evaluated: maternal age, previous gestations, parity, past or family history of preeclampsia, gestational age at the onset of preeclampsia, gestational age at delivery and birth weight. The following pregnancy and delivery complications will be assessed: placental insufficiency, intrauterine growth restriction, fetal loss (stillbirth) and early neonatal death.