2.1. Consortium on Safe Labor

The CSL was a U.S. retrospective cohort study from 2002 to 2008 that abstracted labor and delivery information from electronic medical records from 19 U.S. hospitals. Data extracted for deliveries at 23 gestational weeks or later (n = 228,438) included: maternal socio-demographic characteristics, medical, reproductive and prenatal history, labor and delivery summaries, postpartum and newborn data [66]. For these analyses, we excluded multifetal pregnancies (n = 5,063, 2.2%), mothers with thyroid disease (n = 3,772, 1.6%), mothers with other autoimmune disease (n = 1,764, 0.7%) such as unspecified diseases of connective tissue, thrombophilia, hemorrhagic conditions, ulcerative colitis, coeliac disease, Grave’s disease and Hashimoto’s thyroiditis, and participants from one site for which ICD-9 codes were not reported and no cases of the autoimmune diseases of interest were identified (n = 12,318, 5.3%). Our final analytic sample included 205,521 deliveries. Institutional Review Boards approval was obtained at all participating sites and data are de-identified.