by Dyanne Ahn | Edited by Maryam Kamel
In her book The Maternal Imprint: The Contested Science of Maternal-Fetal Effects, Harvard University historian and philosopher of science Sarah S. Richardson claims that “our bodies are at once biological and social.” Richardson’s viewpoint reflects the recent rise of research in fetal origins science and epigenetics, for studies on human biological variation and determinants of health have begun to incorporate social factors into models that have previously been solely based on gene-centric views.
The Dutch Hunger Winter Study contributed critical insight into intrauterine exposures that lead to long-term health consequences. For instance, the study revealed that babies whose mothers were exposed to famine during early gestation experienced a higher prevalence of obesity than those born before or after World War II and those exposed to famine during mid-to-late gestation. In addition to increasing the incidence of obesity, scientists found that prenatal famine exposure influenced survival rates and led to an increased risk for cardiovascular diseases and cancer. Furthermore, research on intergenerational transmission of trauma revealed that children born to mothers who experience trauma during pregnancy are at a higher risk for developing psychiatric disorders if exposed to stressful or traumatic conditions. Neuroscientist Rachel Yehuda, who has studied the infants of mothers who survived the Holocaust or were exposed to the World Trade Center attacks during pregnancy, attributes this observation to infants being gestated in a high cortisol environment, which results in fetuses having reduced cortisol levels after birth.
Today, the long-term effects of the intrauterine environment on maternal pregnancy are elucidated by various diseases that reveal the association between social inequalities and health. In The Maternal Imprint, Richardson refers to Christopher Kuzawa and Elizabeth Sweet’s journal article, which points to prenatal environmental factors as one of the causes for the observed racial health disparities in cardiovascular disease. The high prevalence of cardiovascular diseases (CVD) amongst African Americans has been associated with low birth weight, which results from the exposure of African American women to increased stress during pregnancy. Because the weight of the mother when she was born is a determinant of her child’s birth weight, low birth weight and, in turn, increased risk of CVD permeate across generations in the African American population despite the discontinuation of social and nutritional factors that induce maternal stress physiology.
According to Boston Children’s Hospital, “mothers of lower socioeconomic status are also more likely to have poorer pregnancy nutrition, inadequate prenatal care, and pregnancy complications,” which can lead to babies with lower weights at birth. Consequently, low birth weight increases the risk of developing various adult diseases, such as hypertension, obesity, and insulin resistance. The research done by Hostinar et al. on early-life socioeconomic disadvantage and metabolic health disparities further supports the results of the investigation on fetal origins of adult disease, showing that socioeconomic status is inversely proportional to metabolic syndrome prevalence. In other words, low socioeconomic status is associated with higher metabolic syndrome risk. In her book, Richardson quotes University College London pediatrician and child nutrition expert Jonathan Wells:
If pregnancy is a niche occupied by the fetus, then economic marginalization over generations can transform that niche into a physiological ghetto where the phenotypic consequences are long-term and liable to reproduction in future generations. (6)
Currently, organizations such as the International Society for Developmental Origins of Health and Disease encourage researchers to further explore the fetal and developmental origins of disease. Given the prevalence of intergenerational and socioeconomic factors that continue to exacerbate health disparities, more resources and funds need to be allocated to develop appropriate public health strategies to reduce the risk of preventable, environmentally-induced long-term diseases.