Variation in Birth Outcomes by Mother’s Country of Birth Among Non-Hispanic Black Women in the United States

Abstract

Rates of prematurity (PTB) and small-for-gestational age (SGA) were compared between US-born and foreign-born non-Hispanic black women. Comparisons were also made between Sub-Saharan African-born and Caribbean-born black women and by maternal country of birth within the two regions. Comparisons were adjusted for sociodemographic, health behavioral and medical risk factors available on the birth record. Birth record data (2008) from all states (n = 27) where mother’s country of birth was recorded were used. These data comprised 58 % of all singleton births to non-Hispanic black women in that year. Pearson Chi square and logistic regression were used to investigate variation in the rates of PTB and SGA by maternal nativity. Foreign-born non-Hispanic black women had significantly lower rates of PTB (OR 0.727; CI 0. 726, 0.727) and SGA (OR 0.742; CI 0.739–0.745) compared to US-born non-Hispanic black women in a fully adjusted model. Sub-Saharan African-born black women compared to Caribbean-born black women had significantly lower rates of PTB and SGA. Within each region, the rates of PTB and SGA varied by mother’s country of birth. These differences could not be explained by adjustment for known risk factors obtained from vital records. Considerable heterogeneity in rates of PTB and SGA among non-Hispanic black women in the US by maternal nativity was documented and remained unexplained after adjustment for known risk factors.

Divergent Patterns of Mitochondrial and Nuclear Ancestry Are Associated with the Risk for Preterm Birth

“…The estimated difference in preterm birth risk between infants where there is no divergent ancestry and those with completely divergent ancestry is 7.5%. This number approximates the entire difference in risk between people of European and African American ancestry, 29 but the actual difference in divergent ancestry that we observed between African American and European ancestry infants was much smaller.…”

“…26–28 In addition, studies of immigrant and nonimmigrant mothers of African ancestry have observed that immigrant mothers, who may have less admixture than women whose families have been in the US for many generations, have lower rates of preterm birth. 29,30 One caveat is that environmental exposures and stressors could also be responsible for the difference in preterm birth risk between immigrant and nonimmigrant populations. 29 …”

“…29,30 One caveat is that environmental exposures and stressors could also be responsible for the difference in preterm birth risk between immigrant and nonimmigrant populations. 29 …”

Comparison of black–white disparities in preterm birth between Canada and the United States

“…[32][33][34] Research conducted outside the US has tended to focus more on differences by maternal country of birth as opposed to race or ethnicity, with consistently higher preterm birth risks reported among women born in sub-Saharan Africa and the Caribbean than among women born in France, Canada or the Netherlands. 13,15,35 In the US, foreign-born black women have considerably lower preterm birth risk than native-born black women, 17,36 but it is not known whether this pattern holds in other countries. We detected no advantage in preterm birth risk among foreign-born versus native-born black women in Canada, with our results instead suggesting higher preterm and very preterm birth risk among foreign-born black women than among native-born black women in Canada (preterm birth rate 9.2% v. 8.3%; very preterm birth 2.1% v. 1.4%).…”

“…[13][14][15] Although the magnitude of these differences is smaller than the disparity in preterm births between black and white women in the US, 16 foreign-born black women in the US have been found to be at lower risk of preterm birth than US-born black women. 17,18 In both Canada and the US, socioeconomic conditions at both individual and neighbourhood levels are important predictors of preterm birth. [19][20][21] Although the income gap between black and white people is markedly smaller in Canada than in the US, 22 black populations in both countries have lower education levels, higher unemployment rates and a greater likelihood of living in low-quality neighbourhoods compared with white populations.…”