Institute of Medicine maternal weight gain recommendations and pregnancy outcome in a predominantly Hispanic population.

OBJECTIVES: To describe gestational weight gain patterns by pre-pregnancy weight and trimester of pregnancy, and to examine the risk of preterm birth associated with pre-pregnancy weight and gestational weight gain using various definitions of adequacy based on the Institute of Medicine (IOM) standard.
METHODS: We used data collected prospectively from 8736 pregnant women receiving care in public health clinics in the West Los Angeles area. Pre-pregnancy weight was based on self-report obtained at the initial visit. Maternal weight was measured at each prenatal visit, allowing for the calculation of total weight gain and the rate of weight gain during each trimester.
RESULTS: Women underweight before pregnancy (body mass index less than 19.8) had the greatest risk of delivering preterm (crude relative risk 1.7, P < .05). Similarities in patterns of weight gain were seen between women of low weight and normal pre-pregnancy weight status, as well as between overweight and obese women. Compared to the IOM recommendations for total weight gain, 47.8% of underweight women and 36.6% of normal-weight women gained the recommended amount. In contrast, 52% and more than 75% of overweight and obese women, respectively, had excessive gains. Inadequate weight gain during the third trimester as opposed to excessive gain, defined specifically for each pre-pregnancy weight status, was predictive of preterm birth.
CONCLUSIONS: Weight monitoring during pregnancy continues to have clinical applications for the prediction of poor birth outcomes. Weight gain less than 90% the IOM recommendation in the third trimester may serve as an indicator for identifying women at risk of delivering preterm.