Maternal race and preterm delivery
Abstract Number: 16
Abstract Type: Original Research
Objective: Nonwhite race has been identified as a risk factor for preterm delivery (PTD) but the reason for this is not clear. Limited research has suggested preterm premature rupture of membranes (PPROM), infectious etiologies, and socioeconomic disparities as contributors to increased PTD rates within black populations. The aim of this study was to investigate associations between maternal race and PTD within a low-risk obstetrical cohort.
Methods: This was a secondary analysis of gravidas recruited for participation in a prospective study of genetic effects on PTD. Subjects with singleton pregnancies were identified during antenatal care between 8-20 weeks gestation. Exclusion criteria included multiple gestations and uterine or major fetal anomalies. Baseline demographic, obstetrical, and medical characteristics were obtained. EDD was confirmed using a standardized algorithm considering LMP and sonography. Data were extracted from delivery records. The primary outcome was PTD, defined as delivery at >20 and <37 weeks gestation. Statistical analyses utilized chi-square analysis, student’s t-test, ANOVA analysis, and logistic regression.
Results: Between 5/06 and 6/09, 2219 subjects were recruited. 161 (7.3%) were lost to follow-up, 58 (2.6%) were excluded due to protocol violations, 48 (2.2%) experienced fetal demise or spontaneous loss, and 22 (1.0%) electively terminated. Race was unknown for 1, for a final cohort of 1929. Age, BMI, and nulliparity differed between races. PTD rates differed between races. After regression analysis to adjust for age, parity, PTD history, and BMI, increased PTD risk persisted in black subjects (OR 2.0, 95% CI 1.2-3.3). When PTD was stratified by cause, spontaneous PTD (sPTD) rate was similar between races. PTD due to maternal medical indications (mPTD) differed between races, largely due to maternal preeclampsia (PEC).
Discussion: In a low-risk obstetrical population, black race was associated with increased PTD rate. This effect was driven by maternal health complications – predominantly preeclampsia – implicating maternal health in race-based obstetrical outcome disparities. There was no difference between racial groups with regard to spontaneous preterm delivery, contradicting common perception to the contrary.