Relationship between Inappropriate Weight Gain during Pregnancy and Low Birth Weight, Louisiana, 2001-2004

Background: In 2009, the Institute of Medicine updated recommendations for appropriate weight gain during pregnancy (WG) based on pre-pregnancy body mass index (BMI). Updated recommendations warrant reinvestigating the relationship between WG and low birth weight (LBW). Objectives: To estimate the relationship between WG and LBW and to assess factors associated with inappropriate WG. Methods: Louisiana Pregnancy Risk Assessment Monitoring System (PRAMS) data from 2001-2004 was linked with birth records. Institute of Medicine 2009 recommendations were used to categorize WG into under, appropriate, and over-gaining based on pre-pregnancy BMI categories of underweight (BMI<18.5), normal (BMI=18.5-24.9), overweight (BMI=25-29.9) and obese (BMI≥30). The relationship between WG and singleton LBW (<2500g) and risk factor associations with WG were investigated using chi-square tests and logistic regression in SAS-callable SUDAAN. Results: Only 34.9% (95%CI=33.8%,36.1%) of Louisiana women achieved appropriate WG, with 24.4% (95%CI=23.4%,25.4%) under-gaining and 40.1% (95%CI=39.5%,41.8%) over-gaining. After controlling for multivitamin use, 3rd trimester smoking, drinking before pregnancy, maternal hypertension, previous LBW birth, and gestational age, under-gaining was significantly associated with LBW (OR=2.28, 95%CI=1.60, 3.25). After controlling for race and gestational age, pre-pregnancy BMI was the only modifiable risk factor for under-gaining (underweight OR=1.35 95%CI=1.09,1.66 and obese OR=0.67 95%CI=0.57,0.78 versus overweight OR=0.41 95%CI=0.35,0.49). Conclusions: Two-thirds of Louisiana women failed to gain the recommended amount of weight during pregnancy. Inappropriate WG is significantly associated with LBW, with women who were underweight before pregnancy being more likely to undergain the appropriate amount during pregnancy. Campaigns should target underweight women in promoting appropriate weight gain during pregnancy.