The Late Preterm Birth Rate and Its Association with Comorbidities in a Population-Based Study

We sought to identify rates, associated morbidities, and preventable causes of late preterm birth (LPB) in a defined population. We conducted a retrospective cross-sectional analysis using deidentified delivery data for all who delivered in San Antonio/Bexar County, Texas between 2000 and 2008 (n = 259,576).LPB was defined as a live birth from 34 (0)/(7) to 36 (6)/(7) weeks. Variables analyzed included age, race/ethnicity, weight gain, hypertensive disease, diabetes, and preterm labor including premature rupture of membranes. From 2000 to 2006, the LPB rate in San Antonio/Bexar County, Texas, was slightly higher than the national average, 9% versus 8.7% (p < 0.01). From 2000 to 2008, 23,312 LPBs occurred in San Antonio/Bexar County and 53% experienced at least one studied comorbidity. Using logistic regression comparing LPB to term, variables associated with an increased risk of LPB were black race, age <17, age >= 35, gestational hypertension, eclampsia, chronic hypertension, and diabetes. LPB was higher than the national average in our population, and preventable causes of LPB (extremes of age, hypertensive disease, and diabetes) were commonly associated with LPB. We speculate that teenage pregnancy prevention, counseling regarding risks associated with advanced maternal age, and improved management and prevention of hypertensive disease and diabetes should prove beneficial in decreasing the LPB rate.