INTRODUCTION:Women ≥40 years old at delivery are increasing and older women are at higher risk for adverse pregnancy outcomes. We sought to evaluate delivery outcomes in these women. METHODS:We conducted an IRB exempt, retrospective cohort study using data from a multi-center quality initiative. Nulliparous singleton births between 1/2012-12/2017 at participating hospitals were included. Patients with intrapartum transfers, missing birth data, or missing/implausible data for maternal age were excluded. Age was stratified into 4 groups12-19 years, 20-29 years, 30-39 years, and 40-55 years. Rates of delivery outcomes were compared between women aged 20-29 years and 40-55 years using a χ2 test. Adjusted relative risks were calculated after controlling for obesity (body mass index ≥30), race-ethnicity, and chronic hypertension. RESULTS:There were 48,093 nulliparous singleton births at 20+0 to 42+6 weeksʼ gestation. After exclusions (n=1891) were removed, the cohort included 46,202 births36,146 (78.2%) in 20-29 years and 1155 (2.5%) in 40-55 years groups. Only 33% of older women achieved a spontaneous vaginal birth, compared to 62% of women age 20-29 (p<0.001). This difference is primarily due to high cesarean delivery (CD) rate (57.7%) in older women, with 25.8% of older women never attempting vaginal birth. Older women are at significantly higher risk of having a CD for all major indications with only a minority (2.8%) of older women having a non-medically indicated CD. CONCLUSION:Older women have an over 50% risk of CD with lower rate of attempting and achieving vaginal birth. This can be useful in counseling about delivery expectations.