THE ISSUE: Anticardiolipin antibodies are positive in certain percentage of pregnancies complicated by adverse pregnancy outcome (severe early-onset preeclampsia, fetal growth restriction, fetal demise, and recurrent miscarriage). There is controversy about which women to screen, what is considered a positive test, and who to treat in subsequent pregnancies. Despite lack of level I evidence for benefit, a recent American College of Obstetricians and Gynecologists practice bulletin recommends using heparin and aspirin throughout pregnancy and for 6 weeks’ postpartum in pregnant women with 1 fetal loss or 3 or more miscarriages in association with positive anticardiolipin antibodies.