Association Between Maternal Weight Gain and Birth Weight

Abstract

OBJECTIVE: To investigate the association between maternal weight gain and birth weight less than 3,000 g and greater than or equal to 4,000 g in underweight (body mass index [BMI] less than 19.8 kg/m²), normal weight (BMI 19.8–26.0 kg/m²), overweight (BMI 26.1–29.0 kg/m²), and obese (BMI greater than 29.0 kg/m²) women, with emphasis on the use of the American Institute of Medicine (IOM) recommendations in Denmark. METHODS: We analyzed data from 2,248 women with singleton, term pregnancies. The relationship between weight gain and risk of birth weight less than 3,000 g and greater than or equal to 4,000 g was examined in the four BMI groups, and use of IOM recommendations was tested by logistic regression analyses. RESULTS: We found an inverse relationship between maternal weight gain and the proportion of infants with a birth weight less than 3,000 g. Birth weight greater than or equal to 4,000 g increased with an increasing weight gain in underweight and normal-weight women, but the association was less apparent in overweight and obese women. Underweight women seemed to benefit from gaining more weight than recommended by the IOM, because the odds ratio (OR) of birth weight less than 3,000 g was 0.3 (95% confidence interval [CI] 0.1–0.9) and the OR was 1.7 for birthweight greater than or equal to 4,000 g (95% CI 0.8–3.6). The normal-weight women had an increased risk of birth weight less than 3,000 g (OR 2.4, 95% CI 1.5–3.7) if weight gain was below the recommended range, and the OR of birth weight greater than or equal to 4,000 g was 1.9 (95% CI 1.5–2.5) when the women gained more than recommended. CONCLUSION: The IOM recommendations may provide a basis for Danish recommendations to pregnant women, although the upper recommended limit for underweight women may have to be increased. LEVEL OF EVIDENCE: II