We sought to characterize complications of pregnancy, labor, and delivery associated with maternal asthma in a contemporary US cohort. We studied a retrospective cohort based on electronic medical record data from 223,512 singleton deliveries from 12 clinical centers across the United States from 2002 through 2008. Women with asthma had higher odds of preeclampsia (adjusted odds ratio [aOR], 1.14; 95% confidence interval [CI], 1.06-1.22), superimposed preeclampsia (aOR, 1.34; 95% CI, 1.15-1.56), gestational diabetes (aOR, 1.11; 95% CI, 1.03-1.19), placental abruption (aOR, 1.22; 95% CI, 1.09-1.36), and placenta previa (aOR, 1.30; 95% CI, 1.08-1.56). Asthmatic women had a higher odds of preterm birth overall (aOR, 1.17; 95% CI, 1.12-1.23) and of medically indicated preterm delivery (aOR, 1.14; 95% CI, 1.01-1.29). Asthmatics were less likely to have spontaneous labor (aOR, 0.87; 95% CI, 0.84-0.90) and vaginal delivery (aOR, 0.84; 95% CI, 0.80-0.87). Risks were higher for breech presentation (aOR, 1.13; 95% CI, 1.05-1.22), hemorrhage (aOR, 1.09; 95% CI, 1.03-1.16), pulmonary embolism (aOR, 1.71; 95% CI, 1.05-2.79), and maternal intensive care unit admission (aOR, 1.34; 95% CI, 1.04-1.72). Maternal asthma increased risk for nearly all outcomes studied in a general obstetric population.