Objective. To estimate the national occurrence of pregnancies in women with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) and to compare pregnancy outcomes in these patients with those in women with pregestational diabetes mellitus (DM) and with the general obstetric population.Methods. We studied the 2002 Nationwide Inpatient Sample of the Healthcare Cost and Utilization Project to estimate the number of obstetric hospitalizations, deliveries, and cesarean deliveries in women with SLE, RA, pregestational DM, and the general obstetric population. Pregnancy outcomes included length of hospital stay, hypertensive disorders including preeclampsia, premature rupture of membranes, and intrauterine growth restriction.Results. Of an estimated 4.04 million deliveries, 3,264 occurred in women with SLE, 1,425 in women with RA, and 13,574 in women with pregestational DM. Women with SLE, RA, and pregestational DM had significantly increased rates of hypertensive disorders compared with the general obstetric population (23.2%, 11.1%, 27.4%, and 7.8%, respectively), longer hospital stays, and significantly higher risk of cesarean delivery. Although women with SLE, RA, and pregestational DM were significantly older than women in the general obstetric population, disparities in the risk of adverse outcomes of pregnancy remained statistically significant after adjustment for maternal age.Conclusion. To our knowledge, this is the first study to examine national data on pregnancy outcomes in women with common rheumatic diseases. As with underlying pregestational DM, women with SLE and RA appear to have a higher age-adjusted risk of adverse outcomes of pregnancy and longer hospital stays than do pregnant women in the general population, and careful antenatal monitoring should be performed.Systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) are chronic autoimmune diseases that have a strong female predominance and commonly affect women of childbearing age. The prevalence of SLE in the US is estimated to be ϳ1-4 per 1,000 women (1,2), with the peak age at onset during the childbearing years. Studies have consistently shown that women comprise 90% of all lupus patients. With the exception of premature ovarian failure due to therapy with alkylating agents, fertility rates for women with SLE are normal (3). Pregnancy outcomes in women with SLE have been studied extensively in specialty clinic settings, and the results have been mixed with regard to the effects of pregnancy on disease flares in women with SLE (4,5). Most, although not all, studies have shown an increased occurrence of pregnancy loss, premature delivery, and preeclampsia in pregnant women with SLE (6-10). The majority of studies examining SLE pregnancies have been prospective or retrospective analyses of pregnant women followed up at tertiary-care academic centers and may not reflect the spectrum of pregnancy experiences across the country (6-10). Furthermore, because of the small number of pregnant patients at any given center or hospital ...