Combined effects of prepregnancy body mass index and weight gain during pregnancy on the risk of preterm delivery.
BACKGROUND
The association between excessive gestational weight gain and preterm delivery is unclear, as is the association between low gestational weight gain and preterm delivery among overweight and obese women.


METHODS
Using data from the Pregnancy Risk Assessment Monitoring System in 21 states, we estimated the risk of very (20-31 weeks) and moderately (32-36 weeks) preterm delivery associated with a combination of prepregnancy body mass index (BMI) and gestational weight gain among 113,019 women who delivered a singleton infant during 1996-2001. We categorized average weight gain (kilograms per week) as very low (<0.12), low (0.12-0.22), moderate (0.23-0.68), high (0.69-0.79), or very high (>0.79). We categorized prepregnancy BMI (kg/m) as underweight (<19.8), normal (19.8-26.0), overweight (26.1-28.9), obese (29.0-34.9), or very obese (>or=35.0). We examined associations for all women and for all women with no complications adjusting for covariates.


RESULTS
There was a strong association between very low weight gain and very preterm delivery that varied by prepregnancy BMI, with the strongest association among underweight women (adjusted odds ratio = 9.8; 95% confidence interval = 7.0-13.8) and the weakest among very obese women (2.3; 1.8-3.1). Very low weight gain was not associated with moderately preterm delivery for overweight or obese women. Women with very high weight gain had approximately twice the odds of very preterm delivery, regardless of prepregnancy BMI.


CONCLUSIONS
This study supports concerns about very low weight gain during pregnancy, even among overweight and obese women, and also suggests that high weight gain, regardless of prepregnancy BMI, deserves further investigation.
National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, GA, USA. pad8@cdc.gov
Patricia M
PM
Dietz
William M
WM
Callaghan
Mary E
ME
Cogswell
Brian
B
Morrow
Cynthia
C
Ferre
Laura A
LA
Schieve
D000293:Adolescent; D000328:Adult; D015992:Body Mass Index; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D011247:Pregnancy / Q000502:physiology*; D047928:Premature Birth; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D015430:Weight Gain