Preterm birth is the leading cause of infant mortality and neonatal morbidity. Maternal obesity is associated with an increased risk of gestational diabetes and hypertensive disorders of pregnancy, which can, in turn, contribute to medically indicated preterm birth. As such, pre-pregnancy obesity represents a potentially modifiable risk factor for adverse neonatal outcomes. In this population-based cohort study, researchers used nationwide data from the US National Vital Statistics System (2016-2017) to study all mothers who had a singleton birth without pre-existing hypertension or diabetes, and examine the association between pre-pregnancy obesity and preterm birth. In studying 7,141,630 singleton live births, researchers found that maternal pre-pregnancy obesity was significantly associated with an increased risk of preterm birth (OR 1.18, 95% CI 1.18 to 1.19). Interestingly, in non-Hispanic white women, maternal obesity was found to be inversely associated with preterm birth in women younger than 20 years (OR 0.92, 95% CI 0.88 to 0.97), and positively associated with preterm birth where maternal age was 20 years or older; the latter was evident in women age 20-24 years, 25-29 years, 30-34 years, 35-39 years, and over 40 years of age. In Hispanic women, maternal obesity was not associated with preterm birth amongst women age less than 20 years, however, a positive association was seen with increasing age. In black women, maternal obesity was inversely associated with preterm birth for women younger than 30 years, and positively associated with preterm birth in those age 30 years or older. This study therefore shows that, in general, maternal pre-pregnancy obesity is significantly associated with an increased risk of preterm birth, with differences in this association occurring with age, race, and/or ethnicity.
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