Infant mortality (the death of a child before the age of 1) is often viewed as an indicator of a society’s overall health, and the United States has a growing discrepancy between its racial/ethnic groups. The highest rate of infant mortality in the United States, according to the CDC, is among non-Hispanic blacks with a rate of 11.4 per 1,000 live births for 2016. This is more than twice the rate for whites with a rate of 4.9 per 1,000 live births. Rhode Island has an infant mortality rate of 9.5 per 1,000 births for African American and 4.4 for white infants, reflecting the national trend.
Both prematurity and low birth weight are strong determinants of first year mortality. This helps explain the difference in infant mortality rates as African American infants are more likely to be premature and have low birth weight. But what is causing black infants in America to have higher rates of prematurity and low birth weight? Researchers at the children’s hospital in Chicago recently published a review in Seminars in Perinatology of the current understanding of this issue.
Socioeconomic factors, such as level of educational attainment, income level, access to healthcare and personal behaviors (cigarette smoking, alcohol and drug use, inadequate prenatal care), are known risk factors for preterm birth and low birth weight. However, researchers have found that these factors alone do not fully explain the difference in infant mortality rate between the races. They note that the disparity in birth outcomes does not improve as a mother’s socioeconomic status, medical status and personal behavior patterns improve. College graduated African American mothers who received adequate prenatal care, for example, still have twice the likelihood of having a low birth weight infant than their white counterparts.
Genetic variation between African American and white mothers was argued by some investigators as a reason for the disparity in birth outcomes. This now seems unlikely, however, since researchers have found genetic variation between races to be much more limited than previously thought. And researchers have found that sub-Saharan African born immigrant mothers in the US have a similar low birth weight rate to that of white mothers and lower rates than African American mothers who have lived their entire lives in the US. This is evidence for minority status throughout life rather than genetic makeup being a risk factor for adverse birth outcomes.
Researchers are exploring several avenues of thought to explain this, one of which is the effect neighborhood poverty has. Neighborhood poverty in adulthood, which African American mothers have a higher likelihood of experiencing, has been shown by researchers to be a risk factor for low birth weight and prematurity independent of the mother’s individual income level. Studies in done in Plymouth, England, the US and Canada have found women living in the most deprived neighborhoods have increased risk of prematurity and low birth weight.
Another possible contributing factor is early-life (fetal) programming of reproductive potential. Women (both black and white) have a higher rate of having a low birth weight infant and preterm delivery if they themselves were born with a low birth weight. This suggests a programming of reproductive physiology during pregnancy in response to stress. Low birth weight female infants may be predisposed to deliver preterm infants themselves once they reach adulthood. Thus, the risk of delivering a preterm or low weight infant can be inherited from a woman’s experience in utero. This phenomenon has been researched with the Dutch famine in 1944-1945, and data suggests that a full two generations of successive non-impoverishment is necessary to reverse this effect.
Finally, researchers are uncovering the direct effects racism has on the health of African American mothers. Chronic exposure to stress from interpersonal racial discrimination can accumulate over time and lead to an enhanced inflammatory response, compromised fetal development and adverse pregnancy outcomes. Institutional racism, which involves multiple systems (education, health care, housing, justice, labor) is getting more attention from researchers as a factor affecting African American birth outcomes. Racial residential segregation and the multiple neighborhood disadvantages it causes has also been associated with higher rates of low birth weight, preterm delivery and infant mortality in African American mothers.
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