Trends in pregnancy weight gain within and outside ranges recommended by the Institute of Medicine in a WIC population.

To examine the proportion of women with a pregnancy weight gain below, within, and above ranges recommended by the Institute of Medicine from 1990 to 1996. Our study population included women attending Special Supplemental Nutrition Program for Women, Infants and Children (WIC) clinics in five states who delivered a liveborn singleton infant at term (N = 120,531). Pregnancy weight gain was self-reported at the postpartum visit. Only 34% of women gained weight within recommended ranges and there was little change in this proportion from 1990 to 1996. The proportion of women gaining less than their recommended weight decreased from 23.4% to 22.0%, and the proportion gaining more than recommended increased from 41.5% to 43.7% during the study period. Stratified analyses revealed similar trends within all race-ethnicity, age, parity, trimester of WIC initiation, and trimester of prenatal care initiation strata and among women in low, average, and high prepregnancy body mass index categories. There was no change in the weight gain distribution among obese women. Absolute and relative increases in the proportion of women gaining more weight than recommended were greatest among women who were underweight, Asian or Native American, less than 20 years of age, multiparous, and who initiated WIC and prenatal care in the third trimester. Pregnancy weight gain increased among this population of WIC participants from 1990 to 1996.