Obesity in older mothers, gestational weight gain, and risk for preterm phenotypes estimates

Objective: To assess whether advanced maternal age modifies the relationship between maternal pre-gravid weight status, gestational weight gain patterns, and the occurrence of spontaneous preterm birth (SPB) and medically indicated preterm birth (MIPB). Methods: Retrospective cohort analysis of vital statistics data from the state of Florida for the period 2004 through 2007 comprising 311,422 singleton pregnancies (two age groups: 20-24 years old or younger women and >= 35 years or older women). Mothers were classified into five clusters based on their pre-pregnancy body mass index (BMI) values: non-obese (less than 30), class I obese (30.0 <= BMI <= 34.9), class II obese (35.0 <= BMI <= 39.9), class III obese (40 <= BMI <= 49.9), and super-obese (BMI >= 50.0). Results: MIPB occurred more frequently among older than younger women [11.8% vs. 6.4%, respectively (p < 0.0001)) whereas SPB occurred more frequently among younger women [11.3% vs. 10.5%, respectively (p < 0.0001)). Maternal obesity increased the risk for MIPB but not for SPB. Regardless of BMI status, the risk of MIPB was elevated among older mothers, particularly among those with suboptimal (<0.23 kg/week) and supraoptimal (>0.68 kg/week) gestational weight gain. A dose-response relationship with increasing gestational weight gain was evident (p < 0.01); the greatest risk for MIPB occurred among older mothers with weekly gestational weight gain in excess of 0.79 kg (OR = 7.76, 95% CI = 5.73-10.5). Conclusion: The occurrence of medically indicated preterm birth is positively associated with increased maternal pregravid body weight, older maternal age and extremes of gestational weight gain. Targeted pre- and inter-conception weight management efforts should be particularly encouraged in older mothers. (C) 2010 Elsevier Ireland Ltd. All rights reserved.