Birth weight and body composition of neonates born to Caucasian compared with African-American mothers.

Objective: To estimate whether neonates of African-American women have lower birth weights because of either decreased lean body mass or fat mass.

Methods: A secondary analysis of a cohort of 104 African-American and 274 Caucasian term, singleton, healthy pregnancies. Women with existing or gestational diabetes were excluded. Neonatal body composition was estimated using anthropometric measurements.

Results: There were significant differences in maternal age (29.5 compared with 25.8, P<.001), prepregnancy body mass index (26.2 compared with 30.9 kg/m, P<.001), and weight gain during pregnancy (15.2 compared with 13.4 kg, P=.03) in Caucasian compared with African-American women, respectively. After adjusting for these factors, African-American women's neonates had significantly lower birth weights (3.20 compared with 3.36 kg, P=.003), less lean body mass (2.80 compared with 2.94 kg, P=.002), but no difference in fat mass (392 compared with 417 g, P=.078).

Conclusion: Decreased birth weight in African-American neonates is due to lower lean body mass and not a difference in adiposity.