Impact of adherence to new IOM weight gain guidelines on birth outcomes among obese pregnant women

Abstract

The new Institute of Medicine (IOM) guidelines for weight gain during pregnancy have been released recently. These guidelines now include an upper limit for weight gain among obese women. However, the impact/feasibility of adhering to these new guidelines remains to be evaluated. The objective of this study was to compare birth outcomes as well as fat mass gain among obese pregnant women during the second half of pregnancy. Fifty‐four women (early pregnancy BMI ≥30) were enrolled at 20wks gestation. Weight, height and body density (using air plethysmography) were measured at 20, 28 and 34 weeks gestation. Body fat then was estimated using Van Raaij's equations (Van Raaij, 1988). Birth information (weight, length and gestational age) were recorded. Weight gain rate was determined and used to categorize women into 3 groups: less than (L), within (W) or above than (A) recommended. On average, women gained 1.2± 2.9 kg between 20–34wk. Twenty‐seven percent had a weight gain rate below recommendations, while 29% was within and 19% was above recommended. Fat mass gain was significantly lower among L group, when compared to W and M (median±InterQ range: L: −0.3 ± 5.11kg; W: 1.6±2.89 and A: 2.7±2.1; p< 0.030). However, no differences were found on birth weight or length after controlling for gestational age at birth. Our preliminary results suggests that higher weight gain rate during the second half of pregnancy might be related to maternal fat accretion and perhaps not to fetal growth among obese women. Composition of weight gain should be incorporated in studies to further evaluate impact of weight gain on maternal and fetal outcomes.