Antepartum bed rest: maternal weight change and infant birth weight

Despite lack of evidence for effectiveness, obstetricians in the United States prescribe antepartum bed rest for more than 700,000 women per year. However, in nonpregnant samples, bed rest treatment produces weight loss. This study assessed maternal weight change (gain) during antepartum hospitalization for bed rest treatment; compared appropriateness of infant birth weights for gestational age, race, and gender; and determined whether maternal weight change predicted infant birth weight. The convenience sample for this longitudinal study consisted of 141 women with high-risk pregnancies who were treated with hospital bed rest. Weekly rate of pregnancy weight change by body mass index was compared with Institute of Medicine recommendations for rate of pregnancy weight gain. Infant birth weight was compared with current US infant birth weights for matching gestational age, gender, and race. Weekly antepartum weight change was significantly lower than Institute of Medicine recommendations (P < 0.001). Infant birth weights were also significantly lower than the national mean when matched for each infant's gestational age, race, and gender (P < 0.001). Maternal weight change predicted infant birth weight (P = 0.05). Bed rest treatment is ineffective for improving pregnancy weight gain. Lower infant birth weights across all gestational ages suggest that maternal weight loss during bed rest may be associated with an increased risk of fetal growth restriction. A randomized trial comparing women with high-risk pregnancies who are ambulatory with those on bed rest is needed to determine whether bed rest treatment, underlying maternal-fetal disease, or both influence inadequate maternal weight gain and poor intrauterine growth.