Police killings of unarmed Black people can have detrimental effects on individuals in the community at large. But according to a new study published in Science Advances, these deaths may also impact unborn babies. Black women who live near the locations of such traumatic events are more likely to give birth to babies who weigh less than 5 pounds, 8 ounces, the low end of what’s considered normal for newborns, reports the American Association for the Advancement of Science (AAAS).

For the investigation, Joscha Legewie, PhD, an assistant professor of sociology at Harvard University, linked statistics from 3.9 million births in California with data on 1,891 police killings in the state between 2005 and 2017. This information included 164 cases involving unarmed Black victims.

Results showed that Black women who were exposed to police killings of unarmed Black individuals within one kilometer (.6 miles) of their residence were more likely to give birth to newborns with birth weights reduced by 50 to more than 80 grams (1.76 to more than 2.82 ounces). This occurred only for fetuses in the first or second trimester at the time of these incidents—not for those in the third trimester.

A baby with a lower than usual birth weight or a fetus that is smaller than usual for its gestational age (number of weeks of pregnancy) can face risk of death at infancy, impaired cognitive ability and ADHD (attention deficit hyperactivity disorder), among other problems.

These study findings demonstrate how structural racism and discrimination can affect the next generation of Black people before they are even born, said AAAS. (Previous research has shown that stress during early pregnancy can increase production of a stress-related hormone that contributes to low birth weight and gestational age.)

In order to distinguish the effects of police killings of unarmed Black people from other factors, AAAS reports, Legewie compared the data on pregnant women exposed to police violence against both armed and unarmed Black people as well as both armed and unarmed white and Hispanic people.

Legewie also contrasted birth weight and gestational age for Black infants in areas exposed to police killings of unarmed Black people before and after birth. He controlled for genetic and family factors by comparing the health of infants born to siblings who either were or weren’t exposed to police killings during pregnancy. But he noted that only the killings of unarmed Black people appeared to generate perceptible health problems for Black infants in utero.

“I find that the effect of police killings is unique to unarmed Black victims, which makes me confident that this is not just general violence and crime,” he said. “No, the effect seems to be driven by the perceived injustice, discrimination and fear related to police killings of unarmed Black victims.”

Legewie suggested that future research should follow Black women throughout their pregnancies to document episodes of discrimination they faced—including police violence in their neighborhoods—and to explore the stress and anxiety caused by such experiences. 

For related coverage, read “Racism May Place Black Mothers at a Higher Risk of Death.”