Abstract
Objective Preterm delivery for preeclampsia or placental insufficiency (PREPI) is a clinical criterion for antiphospholipid syndrome (APS), but no prior prospective studies have used the international classification criteria for APS. Our objective is to determine the proportion of women with PREPI who test positive for aPL using international criteria for antiphospholipid antibody (aPL) assays. Methods We conducted a prospective, case-control study of 148 women delivered < 36 weeks because of PREPI compared to 148 controls. PREPI cases delivered < 36 weeks were compared to matched controls. Cases and controls were tested for aPL. Demographic variables were compared with chi-squared and Wilcoxon-rank-sum statistics. Rates of + aPL were compared using adjusted odds ratios (aORs) for maternal body mass index (BMI) and Caucasian race. Positive aPL (+aPL) was defined as lupus anticoagulant (LA), anticardiolipin (aCL) immunoglobulin G (IgG) (GPL) or immunoglobulin M (IgM) (MPL) ≥ 40, or anti-β2-glycoprotein I (aβ2GPI) IgG (SGU) or IgM (SMU) ≥ 40. Results Controls were more likely to be Caucasian (87% vs 70%, p = 0.006) and had lower BMIs (BMI 26 vs 33, p < 0.001). Positive aPL were found more commonly in cases than controls (11.5% vs 1.4%, aOR 8.9 (95% CI 1.9-41.4)). In + aPL cases, 76% had + LA, 41% had + aCL, and 24% had + aβ2GPI. Conclusion Women requiring early delivery for PREPI are more likely to have aPL (and thus APS) than controls. This is the first prospective study using both obstetric definitions and laboratory criteria in accordance with APS international criteria.