Study links socioeconomic stressors to worse pregnancy outcomes for black women

Stresses experienced by black women, such as socioeconomic inequalities, may alter key processes in the body that predispose them to worse pregnancy outcomes than white women, a study by the University of Cambridge has found.

These altered physiological processes may lead to higher rates of preeclampsia in black women, and higher rates of preterm birth and fetal growth restriction in black babies, compared to white women and their babies.

In a major review of published studies, the researchers looked at a range of processes that are vital in the body during pregnancy - including the control of inflammation, and blood flow to the developing fetus. They found these processes are often altered in ways linked to poorer pregnancy outcomes in black women, compared to white women.

These are not the result of genetic differences between black and white women. Instead, the results suggest that persistent socio-environmental stressors - known to have a measurable biological effect - may influence the body's ability to function healthily during pregnancy.

Black women and their babies face significantly higher health risks during pregnancy and childbirth than white women. Black women in the UK are 2.7 times more likely to die during pregnancy compared with white women, and black babies are more than twice as likely to die before their first birthday as white babies.

Until now, the biological pathways that may help explain the link between socioeconomic inequalities and poorer pregnancy outcomes in black women have received little attention.

"Pregnancy and childbirth put great stress on a woman's body. Black women may experience additional strain due to factors including systemic racism, socioeconomic disadvantage and environmental stressors. During pregnancy, this strain may affect key biological processes in ways that increase the risk of conditions such as pre-eclampsia," said Grace Amedor, first author of the study, who conducted the work as part of her medical studies at the University of Cambridge.

Amedor, now a resident doctor, added: "I wanted to investigate after I read that black women were much more likely to die in, or just after, pregnancy than white women. As a black woman myself that was scary to hear. I was surprised that although this disparity had been known for a long time, there was little research into the potential underlying physiological reasons."

Preeclampsia in pregnancy causes a woman to have very high blood pressure, which can lead to seizures and - in some cases - death. It can also lead to fetal growth restriction, when the baby doesn't grow properly in the uterus, and pre-term birth, when a baby is born earlier than it should be.

The report is published today in the journal Trends in Endocrinology & Metabolism.

Three key physiological differences

The researchers identified three key physiological mechanisms that affect pregnancy outcomes, and show measurable differences between black and white women:

Increased uteroplacental vascular resistance: This is a tightening of blood vessels that can reduce blood flow to the placenta. Their review identified differences in biological markers linked to this process, which may help explain higher rates of pre‑eclampsia, maternal hypertension, fetal growth restriction and preterm birth in black women.

Higher oxidative stress: Oxidative stress occurs when damaging molecules called reactive oxygen species overwhelm the body's antioxidant defences. The study found that black women often have higher levels of oxidative stress markers and lower levels of protective antioxidants. These imbalances can increase the risk of preterm birth, preeclampsia, and fetal growth restriction.

Greater inflammation: Healthy pregnancy requires a carefully regulated immune response. The study found that black women show higher levels of several inflammation-related markers. These changes have been associated with preterm birth and preeclampsia.

Driving change

The Cambridge team hope their findings could help guide new approaches to reducing the disparity in pregnancy outcomes between black and white women. But they stress that long‑term change depends on addressing the social conditions that give rise to these unequal outcomes.

The significant disparity in pregnancy complications between black and white women is well known and has often been explained in terms of differences in medical care, alongside broader social and environmental inequalities. We've found these exposures can disproportionally affect black women's bodies, making them less able to function healthily during pregnancy."

Professor Dino Giussani, scientist at the University of Cambridge's Department of Physiology, Development and Neuroscience and senior author of the study

"It's important that we don't stop trying to tackle the root causes that lead to worse pregnancy outcomes in black women, which are the socioeconomic disparities and the systemic racism they can experience throughout their lives," said Amedor.