Association between maternal pre-pregnancy obesity and preterm birth according to maternal age and race or ethnicity: a population-based study

The relation between maternal pre-pregnancy obesity and preterm birth is controversial and inconclusive. We aimed to clarify the association between pre-pregnancy obesity and preterm birth by maternal age and race or ethnicity in a large, multiracial, multiethnic, and diverse population in the USA.We did a population-based cohort study using nationwide birth certificate data from the US National Vital Statistics System for 2016 and 2017. We...