The impact of obesity on spontaneous and medically indicated preterm birth among adolescent mothers
We sought to evaluate the impact of obesity on the risk of spontaneous and medically indicated preterm birth in young women compared to adult women.
Florida vital records from 2004 to 2007 were used to obtain data. The study sample consisted of 290,807 mothers of whom 4,739 were adolescent girls ≤15 years old: 23,228 were girls 16–17 years old; 58,196 were women 18–19 years old; and 204,644 were women 20–24 years old. Adjusted estimates for spontaneous and medically indicated preterm birth were determined based on maternal BMI and weight gain during pregnancy. Subjects were categorized by BMI as follows: class I obesity (30.0 ≤ BMI ≤ 34.9), class II obesity (35.0 ≤ BMI ≤ 39.9), class III obesity (40 ≤ BMI ≤ 49.9), and super-obese (BMI ≥ 50.0).
Obese mothers had elevated risk for medically indicated preterm birth and lower risk for spontaneous preterm birth compared to non-obese mothers. Overall, the risk for spontaneous preterm birth increased in a dose-dependent fashion with younger age but no age-dependent trend was observed for medically indicated preterm birth (P < 0.0001). Very low weight gain (<0.12 kg/week) during pregnancy was associated with a higher risk of spontaneous preterm birth among both non-obese and obese teenagers.
Preterm birth is a heterogeneous entity that is mediated by obesity status and maternal age. Obesity among pregnant teenagers increases the risk for medically indicated preterm birth but not the risk for spontaneous preterm birth.