Effect of caloric balance during pregnancy on weight gain and birthweight: Diana project results

Studies on the effects of caloric (kcal) intake on prenatal weight gain and birthwelght show mixed results. Lack of agreement is likely related in part to a failure to determine kcal balance. The purpose of this study is to assess the influence of kcal intake and energy expenditure (EE) during pregnancy on weight gain (WG) and birth weigh t (BW). Subjects were 520 participants in the Diana Project fdlowed prior to conception to 8 weeks postpartum. Women completed food frequency questionnaires (Willett) and 7 day activity records monthly, and measured their weight weekly. Other data were obtained. EE from physical activity was calculated in mets. In this primarily Caucasian, middle income sample, mean kcat intake rose from 1780 prior to pregnancy to 2220 kcal at 160 days postconception. It then plateaued to delivery at approximately 2190 kcal. Peak increase in kcal intake was observed between 20 (mean =1880) and 40 days (mean - 2050) postconception. Mean EE declined by 202 kcal across pregnancy. Multiple regression analysis on birthweight that included major variables known to influence BW and quarterly changes in kcal intake and EE revealed a R2 of 0.36 for a model that retained at p<.05 the variables of gestational age, infant gender; maternal height, age, parity, and waist-to-hip ratio; kcal intake change in qtr. 1, and weight change in qrts. 2 and 3. An increase of 100 kcals in qtr 1 was associated with a 7 g increase in BW, and an increase in weight of 1 Ib. in qtr 2 was associated with a 1 5 g increase in BW. Overall, an increment of 100 kcal was associated with 0.8 Ib. of WG and each 100 mets of EE with a 0.4 Ib. weight loss. These preliminary results suggest that caloric balance influences prenatal WG and BW.