Modifiable Determinants of Birth Weight Variability in Twins

Abstract

Intrauterine growth retardation is a major contributor to the increased perinatal morbidity and mortality reported for twins. Prenatal factors influencing intrauterine growth were evaluated in 80 women followed in a special antepartum Twin Clinic. The mean birth weight was calculated for each twin set and normalized to gestational age specific birth weight centiles. The mean birth weight centile was 32.9 ± 24, which is significantly less than the mean for singletons (P <. 001). Multiple demographic, socioeconomic, medical, and nutritional variables were tested to determine their impact on intrauterine growth. A stepwise regression analysis suggested that six variables predict over half of the total variability in the normalized mean birth weight centile (R² = 0.51). Significant variables (P <. 05) included race, gestational age at diagnosis, smoking, prepregnancy weight, percent ideal body weight, and the rate of weekly weight gain. Intrauterine growth in twins was improved with weight gain rate of at least 1.01 ± 52 lb/week resulting in a total maternal weight gain of 38.4 ± 18.3 lb. Gestational age at diagnosis, smoking, rate of weekly weight gain, and prepregnancy weight are important modifiable determinants of intrauterine growth in twins and have a relatively greater impact on intrauterine growth than in singletons.

Key Words:

• Twins
• Intrauterine growth
• Maternal nutrition
• Smoking