Birth Weights of Black African Babies of Migrant and Nonmigrant Mothers Compared With Those of Babies of European Mothers in Portugal

The study aim is to investigate differences in birth weights between babies of foreign-born black African, Portugal-born black African, and Portugal-born white mothers. Hospital records for Amadora and Sintra from July 2001 to June 2002 were collated and 2949 Portugal-born white, 461 Portugal-born black African, and 817 foreign-born black African live singleton babies were identified. The impact of biologic and social factors (infant sex, maternal age, parity, gestational age, and maternal smoking, education, and occupational class) and mode of delivery on birth weights was assessed by using multivariable regression models. African mothers were more likely to be of lower socioeconomic status than white Portuguese mothers, among whom rates of smoking were two to three times greater (21% among white Portuguese mothers). Small preterm babies comprised 1.5% of white Portuguese babies, 2.3% of babies of Portugal-born African mothers, and 3.9% of babies of foreign-born African mothers ( p < 0.05 compared with white Portuguese babies). Compared with white Portuguese babies, mean birth weight of term babies, adjusted for sex, among Portugal-born African mothers was −24.6 g (95% confidence interval, −70.1–20.9), and among foreign-born African mothers, was +38.8 g (95% confidence interval, 2.9–74.8). Adjustment for parity, maternal age, and gestational age decreased the significant birth weight advantage of babies of foreign-born African mothers to +2.3 g (95% confidence interval, −31.9–36.5). Among nonsmokers, after adjusting for these factors, white Portuguese babies were heavier (40 g; p < 0.05) than babies of foreign-born African mothers, but among smokers, they were lighter (163 g; p < 0.05). Compared with white Portuguese babies, mean birth weight of term babies of foreign-born African mothers was greater, and that of babies of Portugal-born African mothers was intermediate. These differences were related to a combination of biologic factors and smoking.