Comparison of risk and protective factors for preterm birth in rural, suburban, and urban Fresno County, California

Abstract

Preterm birth (PTB, < 37 weeks’ gestation) may impose lifelong sequelae or death. Fresno County reports the highest rate of PTB in California. A place-based approach investigating local risk factors for PTB may provide important opportunities for intervention and prevention. In this study, we examine risk and protective factors for PTB in rural, suburban, and urban Fresno County, California. The sample was drawn from Fresno County, California singleton births 2007-2012 (n = 81,021). Multivariate models of maternal risk and protective factors for PTB were stratified by rural, suburban, and urban residence. Women with diabetes, hypertension, infection, fewer than three prenatal care visits, previous PTB, interpregnancy interval less than six months, or were of Black race/ethnicity were at increased risk of PTB. The risk of PTB was highest for women residing in rural locations with preeclampsia superimposed on preexisting hypertension (adjusted relative risk (aRR) 5.7, 95% confidence interval (CI) 4.4-7.4). For women living in urban residences, maternal birth in Mexico and overweight body mass index (BMI) offered protection from PTB (aRRs 0.9), whereas participation in the Women, Infants and Children program was protective for women in either urban or rural residences (aRRs 0.8). Public insurance, <12 year of education,  underweight BMI, and interpregnancy interval of five years or more were risk factors only for women in urban residences. These findings may provide important opportunities for local intervention.