225727 Effect modification of birth weight outcomes and gestational weight gain by pre-pregnancy body mass index in a diverse population

Tuesday, November 9, 2010 : 1:20 PM - 1:35 PM

Tracy Becerra, MPH, OTR/L , Department of Epidemiology, University of California, Los Angeles, Los Angeles, CA
Beate Ritz, MD, PhD , Epidemiology, UCLA, Los Angeles, CA
Obesity and pregnancy weight gain are changing the face of perinatal outcomes. Here I examine how pre-pregnancy body mass index (BMI) and gestational weight gain influence extreme birth weights in Los Angeles County. The 2007 vital records of live births were reviewed to identify infants born preterm low weight (<37 wks gestation and <2500g), term low weight (>37 wks gestation and <2500g), or macrosomic (>4000 g, also >4500g). New variables collected on the birth certificate and the new Institute of Medicine Guidelines (IOM, 2009) were used. Using logistic regression I examined the influence of BMI and gestational weight gain on these outcomes while controlling for other risk factors. Gaining less or gaining more weight than recommended increased the odds for term low birth weight (TLBW) and macrosomia, respectively. BMI modified these associations in opposing directions: highest effect for TLBW among underweight women, [Adjusted Odds Ratio: 2.5 (95% confidence interval: 1.8, 3.4)], followed by normal weight women, 1.7 (1.5, 1.9); highest effect for macrosomia (>4500g) among normal weight women, 3.0 (2.3, 3.8), followed by obese women, 2.3 (1.7, 3.2). Obesity increased the odds of preterm low weight births, 1.2 (1.1, 1.3). Even though African American women were more often overweight and obese (26.2% and 22.5% respectively) and gained more weight during pregnancy (52.2%), they did not exhibit the highest risk for macrosomia (>4000g: 5.2%). Instead, White and Latino women had the highest risks (9.6% and 7.7% respectively). Weight gain during pregnancy affects BMI subgroups and impacts ethnic groups differently.

Learning Areas:
Assessment of individual and community needs for health education
Public health or related research

Learning Objectives:
1. Identify two strong risk factors for macrosomia and term low birth weight 2. Describe the interaction between the two risk factors 3. Compare the interaction effects between macrosomia and term low birth weight 4. Evaluate the mechanisms within each ethnic group that result in different outcomes

Keywords: Pregnancy, Epidemiology

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: I am qualified to present on this topic as I have been training in epidemiology methods for 4 years under a current expert that is a professor in epidemiology at UCLA. She has been reviewing my results and interpretations. I also have a clinical degree and a masters in public health and have experience working directly with the populations in question.
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.