Racism and Birth Inequities, From Biology to Society
Image Credit: UNICEF
Black mothers in the US are 3-4x more likely to die from pregnancy-related causes than white mothers (NPR/ProPublica). In addition, 40.6% of Black births are preterm, compared to 33.1% of white births (CDC). Compounding evidence suggests that the lived experience of racism in the US, rather than genetics, health behaviors (e.g. smoking), or access to health care overwhelmingly contributes to racial disparities in pregnancy related deaths and infant mortality (Christian 2019).
How can this be the case? It is well established that psychological stress can lead to poorer pregnancy outcomes (Staneva 2015). Systemic sources of stress, like racism, can therefore confer pregnancy detriments at a population level. Linking psychological stress to actionable medical targets (e.g. sleep, anxiety, or hypertension) is a challenge for neuroscience and related fields, like psychiatry. At the same time, we can agitate for societal changes that alleviate health inequities faced by Black women and mothers.
How does stress harm pregnancies?
From a biological perspective, we still have a lot to learn about how psychological distress might affect pregnancies, birthing, and future child development. Public health researchers in Australia and the U.K. have drawn a compelling connection between stress and worsened pregnancy outcomes. Using statistical methods to survey a large body of existing health literature, they found that depression, anxiety, and stress during pregnancy increases the likelihood of preterm birth. (Staneva 2015)
Neuroscientists and biologists are working actively to understand precisely how stress damages pregnancies. Their work indicates that the connections between mental health and reproductive ailments are complex and bidirectional. For instance, Ashley Griffin, a neuroscience PhD student at the University of Mississippi Medical Center, led a study finding that acute kidney injury may precipitate cognitive impairment in rats after they give birth (Griffin 2020). Kidney injuries in humans may develop as a result of hypertension-induced preeclampsia. Hypertension, or high blood pressure, is of course strongly linked to psychological stress (Spruill 2010).
In addition, early reports suggest that parental stress may alter offspring neurodevelopment via intergenerational transfer. A fascinating study first-authored by Yasmine Cissé, a postdoctoral scholar at UM Baltimore, indicates that lifetime parental stress in rodents induces genetic changes in both mid-gestation placental tissue and the developing fetal brain (Cissé 2020). These changes are sex-specifc for both the parents and offspring. This means that preconception stress from the mother or father will affect placental and fetal genes in different ways, depending if the offspring is male or female.
The weathering hypothesis
Science tells us that stress changes pregnancies. How might race interplay with the biology of stress to challenge public health? The idea that Black pregnancies incur disproportionate harm due to the systemic stress of racism was first suggested in the early 1990s. Researchers observed that counterintuitively, babies born to Black teen mothers had a survival advantage relative to babies born by Black women in their 20s to early 30s (typically thought of as “prime” childbearing age). For white women of European ancestry, birthing outcomes improve as women age past their teenage years. To explain these findings, Arline Geronimus proposed the weathering hypothesis, which states that Black mothers suffer the physical consequences of accumulated racial discrimination as they enter early adulthood. (Geronimus 1992)
The weathering effect can be further examined with metrics that scientists have developed to quantify the physiological effects of stress. For example, scientists use the term “allostatic load” to refer to the “wear and tear” that everyday stress (in contrast to singular traumatic events) places on the body (McEwen 1999). Allostatic load is calculated per individual by measuring two categories of biomarkers called primary and secondary mediators. The first, primary mediators, are molecules that the body releases immediately upon experiencing stress, including norepinephrine and cortisol. Secondary mediators are downstream targets of primary mediator release, and include things like blood pressure, cholesterol levels, and waist-to-hip size ratio. Using a predetermined algorithm, all of these biomarker measurements can be combined into one numerical allostatic load score. (McEwen 1999, Geronimus 2006)
Allostatic load provides an entry point for connecting societal stratification to human biology. By comparing allostatic load scores across classes of individuals, and combining this information with other statistics (e.g. pregnancy outcomes), we can begin to observe connections between social status and health. Notably, Geronimus et al. reported that Black men and women have a higher mean allostatic load than white people at all ages, and the score differential increases with age. Moreover, the differences in allostatic load cannot be explained by economic status: wealthier Black people have a higher probability of high allostatic load score than poorer white people. (Geronimus 2006)
Black women, on average, bear the brunt of allostatic load when compared with Black men or white women (Geronimus 2006). While strict causality has not been established, the weathering hypothesis becomes increasingly credible when considered alongside allostatic load data — as allostatic load increases with age, Black pregnancies deteriorate at a higher rate. In addition, strong evidence suggests that the higher risk of preterm birth and infant/mother mortality in US Black women is not genetic. When compared with foreign-born Black women from the Caribbean or Africa now living in the United States, US-born Black women have a 3% higher risk of preterm birth (DeSisto 2018). Strikingly, birth weight increases across generations for white US immigrants from Europe, but decreases across generations for Black US immigrants from the Caribbean and Africa (Collins 2002). This is true even when Black women become wealthier and more educated in the generations following their immigration. (Collins 2002, Christian 2019)
Stress and society
What steps could we, as a society, take to decrease the disproportionate toll on Black mothers and babies?
Interestingly, the ongoing COVID-19 pandemic may be able to provide insight on social interventions that could reduce preterm births. Researchers in Ireland and Denmark observed that during the pandemic-induced lockdown, when most new mothers were forced to stay at home prior to giving birth, preterm birth rates dropped sharply. And in particular, dangerous preterm cases that posed imminent harm to mothers and infants were all but eliminated. (Phillip 2020) (Preston 2020, NY Times)
Because these results are so new, researchers still do not understand what factors might have led to improvements in preterm birth rate. Additionally, we still do not have clear data about if and how the lockdown might have impacted preterm birth rates in some areas as opposed to others, and which populations of people were specifically affected. But by examining these results more closely, the pandemic might give us some clues about non-medical strategies that can promote good health and equitable outcomes for new mothers.
Data regarding the pandemic’s effect on preterm birth rates must be considered alongside a recent study from a medical research team in Philadelphia which measured the prevalence of SARS-CoV-2 antibodies in pregnant women (Wu 2020, NY Times). The researchers found that 10% of Black and Latina study participants had antibodies, compared with 2% of white women and 1% of Asian women (Flannery 2020). These results underscore the structural disparities in reproductive health faced by Black and Latina women in the US. When we examine how temporary societal changes may have ameliorated preterm birth rates, we must ask: who benefited? And why?
Advocacy Going Forward
Since 1986, the CDC has systematically collected data pertaining to pregnancy-related deaths in the US. Death certificates for all women who died during pregnancy or within 1 year of pregnancy are voluntarily reported from across the US, and epidemiologists at the CDC compile cause of death information with demographic data (CDC Pregnancy Mortality Surveillance System). Maintaining such a database will be critical for enacting science-based public health policy that prioritizes the needs of Black mothers.
The National Birth Equity Collaborative (NBEC), a non-profit organization founded by Dr. Joia Adele Crear-Perry, works within communities to promote optimal birthing outcomes for Black mothers and babies. The NBEC has put forward a policy agenda that clears a path forward for birth equity in the US. It asserts that health is a right, and that reproductive health and autonomy must be protected at the highest levels of government (NBEC). As we work to embody a more just and equitable society, we must center the health of vulnerable Black mothers and infants.
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