ObjectiveTo determine whether higher levels of anti-β2-glycoprotein 1 before 25 weeks' gestation are independently associated with either pregnancy loss or pregnancy-induced hypertension.MethodsSerum samples for the immunoglobulin (Ig) G and IgM isotypes of anti-β2-glycoprotein 1, anticardiolipin antibody, and antiphosphatidylserine were collected from 325 low-risk nulliparas who presented for prenatal care before 25 weeks' gestation. This cohort was followed prospectively for the development of pregnancy loss and pregnancy-induced hypertension.ResultsThe adjusted odds ratios (OR) and 95% confidence intervals (CI) of elevated antiphospholipid antibody levels for pregnancy loss were: IgG anti-β2-glycoprotein 1, OR 1.2 (CI 0.5, 2.8); IgG anticardiolipin antibody, OR 8.4 (CI 2.3, 31); and IgG antiphosphatidylserine, OR 5.2 (CI 1.4, 18.7). The relative risks of pregnancy loss for all IgG antiphospholipid antibodies were higher among women who had blood collected after 10 weeks' gestation compared with those studied before 10 weeks' gestation. However, there were only marginal differences in the attributable risks, suggesting that the impact of elevated levels of antiphospholipid antibodies might be similar in early and later stages of pregnancy. None of the antiphospholipid antibodies was associated with pregnancy-induced hypertension.ConclusionIn this study, elevated levels of IgG anticardiolipin and IgG antiphosphatidylserine antibodies were markers of pregnancy loss, but an elevated level of anti-β2-glycoprotein was not a strong predictor of fetal loss.