Estimating risk factors for spontaneous preterm delivery in teen pregnancies.

PURPOSE: Our aim was to estimate the perinatal risk factors associated with spontaneous preterm birth in the teenage parturient.

METHODS: In a cohort study of all nulliparous teen (≤18-year old) deliveries over a 4-year period at one institution, we identified all cases of spontaneous preterm birth as defined by non-indicated delivery prior to 37 weeks of gestation. Analysis was performed using Fisher's exact, Student t test and logistic regression modeling.

RESULTS: Of the 650 included teen deliveries, 88 (14 %) cases of spontaneous preterm birth were identified. Teenage mothers with spontaneous preterm birth had a significantly lower body mass index (BMI) (27.2 ± 6.4 vs. 31.0 ± 6.2, p = 0.0001) and had lower gestational weight gain (14.4 ± 6.6 vs. 11.2 ± 5.0 kg, p = 0.0001) than those mothers with uncomplicated term births. In fact, a normal prepregnancy BMI (<25 kg/m(2)) placed the teen at elevated risk for spontaneous preterm birth (OR 3.35, 95 % CI 1.98-5.64), while prepregnancy obesity (30-35 kg/m(2)) was protective (OR 0.26, 95 % CI 0.12-0.58). Controlling for potential confounders such as race, tobacco or illicit drug use, late prenatal care and sexually transmitted infections did not attenuate the above findings.

CONCLUSIONS: Higher prepregnancy BMI, especially obesity, appears to be protective against spontaneous preterm birth in the nulliparous teen parturient. Further studies confirming this finding and investigation of potential underlying mechanisms of this association are warranted.