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

Purpose

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.

Methods

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.

Results

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).

Conclusions

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.

Introduction

The causes and implications of ethnic disparities in birth weights continue to be debated, and evidence from ethnic contrasts in different settings may be informative. For example, in the United States, migrant Mexican mothers are less likely to have low-birth-weight (LBW) infants than white American mothers despite lower socioeconomic status (SES), in contrast to the long-standing picture of lower mean birth weights, more LBW infants, and generally poor perinatal outcomes among US-born African-American women 1, 2, 3, 4. Conversely, migrant Asian Indian mothers in the United States are more likely to have LBW infants despite higher SES (5). Perinatal outcomes appear to be better among infants of migrant mothers than among subsequent generations 1, 2, 6. Differences in behavioral, medical, nutritional, or cultural factors have been suggested to contribute to the perinatal advantage of foreign-born women.

Portugal has a sizeable population of Africans, mainly from its excolonies Cape Verde, Angola, Mozambique, Guinea-Bissau, and San Tome Principe. Most arrived in the late 1970s after independence of their home countries, and the majority reside in Greater Lisbon (7). Compared with other western European countries, Portugal provides an interesting historic, sociopolitical, and economic context in which to examine the impact of migration on health. It has experienced relatively recent dramatic changes in political circumstances since the revolution in 1974 and rapid improvements in standard of living 8, 9. Infant mortality declined from 35 to 5 per 1,000 live births between 1974 and 2002, and maternal mortality, from 45 to 5 per 1,000 in the same period (10).

In Europe, North African–origin babies in Belgium are heavier than Belgian-origin babies (11), but the experience of the United Kingdom is different. Migrant south Asian, black African, and black Caribbean mothers are more likely to have lighter and LBW infants than white United Kingdom–born mothers 12, 13, and there have been no significant changes in birth weights between babies born to foreign-born and United Kingdom–born mothers in the same ethnic group (14).

In this study, we examine whether birth weights of babies of migrant and nonmigrant black African mothers living in Portugal differ from those of white Portuguese mothers.