With deportation and discrimination fears currently on the minds of many in the United States, a University of Michigan study shows that the stress from an historic immigration raid is associated with Latina mothers delivering babies with lower birth weights, and sometimes early.

The U–M School of Public Health and Institute of Social Research team found that after the federal immigration raid in Postville, Iowa, in 2008, Latino babies born in the 37 weeks after the event had a 24 percent greater risk of lower birth weight than babies born the prior year. There also was an increased risk in preterm birth among Latina mothers compared with non–Latina white women.

"While health disparities often are believed to be caused by differences in individual health behaviors, access to health care, or even genetics, our findings implicate the impact of racial/ethnic stereotyping and related psychosocial stressors on health," said Arline Geronimus, research professor at the U–M Institute for Social Research and a professor at the School of Public Health.

Other U–M authors were Nicole Novak of the U–M Institute for Social Research and Aresha Martinez–Cardoso of the School of Public Health.

Their research was featured in the International Journal of Epidemiology.

In one of the largest single–site raids in U.S. history, federal immigration officials used military tactics to arrest 389 employees of a meat–processing plant in the small Iowa community. Ninety–eight percent of those arrested, handcuffed and held in various detention centers were Latino, as all were initially suspected to be undocumented immigrants.

"In the wake of the Postville immigration raid, U.S.–born and immigrant Latino families feared deportations and follow–up raids, and faced increased economic and social marginalization," Novak said. "These stressors permeated the lives of both U.S.–born and foreign–born Latina mothers, potentially activating harmful physiological responses that could result in the poor birth outcomes we documented among their babies."

"Our findings, then, shed light on what is to come for our nation's health if we continue down this road of anti–immigrant rhetoric and continue fueling a deportation regime, including implementing it by criminalizing immigrants and using militaristic tactics," Martinez–Cardoso said.

Psychosocial stressors can affect pregnant mothers by shifting stress hormone balances in ways that affect a developing fetus by triggering premature birth, leading to growth restriction and low birth weight even for babies born at full term, and by reducing social and material support networks that promote a mother's health during pregnancy, the researchers said. Low birth weight is associated with increasing a baby's chance of dying or having long–term health and academic problems.

The researchers obtained all birth certificate data from 2006–10, and their analysis focused on more than 52,000 births of Latina and non–Latina white mothers. They classified infants as exposed to the post–raid environment if they were born in the 37 weeks following the raid. Those born in the same period a year earlier were classified an unexposed.

Total numbers of births among Latina and non–Latina white mothers were nearly the same in the pre– and post–raid periods. No changes were observed in conventional risk factors for low birth weight for either group across the time periods studied.

Prior to the raid, Latina and non–Latina white mothers had similar rates of low–birth weight, at 4.7 percent, and preterm births at 7.5 percent. During the period following the raid, the rates actually went down for white mothers, continuing a nationwide trend started in 2006, but increased for Latina mothers.