UW News

January 14, 2010

Air bags not a risk to pregnant women in motor vehicle crashes, study finds

Center for Sensorimotor Neural Engineering

UW epidemiologist Melissa Schiff has had a long-standing interest in injury in pregnancy and motor vehicle crashes, dating back to her training as a physician specializing in obstetrics and gynecology in Albuquerque, N.M. Schiff said that a pregnant sister of a nurse on staff was killed in a crash. As a faculty member, Schiff subsequently was in charge of a maternal mortality review committee.

Schiff came to Seattle in the late 1990’s to pursue a master’s degree in public health, and wrote her master’s thesis on pregnancy outcomes for women who experience injury. She now works at the Harborview Injury Prevention & Research Center and is a professor of epidemiology at the UW School of Public Health.

She recently led a research team that found that air bags do not seem to elevate risk of most potential adverse outcomes during pregnancy for women involved in motor vehicle crashes. The study results were published in the January 2010 issue of Obstetrics & Gynecology.

Motor vehicle crashes affect an estimated 32,800 pregnant women each year in the United States. Studies have concluded that crashes are one of the leading causes of injury-related maternal and fetal deaths, and the most common cause of injury-related hospitalization among pregnant women.

“No one has conducted any large scale data-driven studies looking at air bags and pregnant women,” said Schiff, the lead author on the study

The findings may seem counterintuitive, but Schiff said she was pleased that there was not an increased risk for pregnant women among many of the outcomes her team examined. Schiff said reports on early model airbags had found the opposite: an increased risk of death among special populations, namely children and small-statured women.

“Air bags are such a ubiquitous part of motor vehicles as a passive safety measure, and public health experts can’t advocate behavior change as a way to alter outcomes,” she said. “Over the years, airbags have been redesigned and have greatly reduced the threat from early models.”

Researchers detected two inconclusive findings: a 70 percent increased risk of preterm labor and a threefold increased risk of fetal death among occupants in vehicles with air-bag deployment. Schiff said these findings are “inconclusive” because of the small sample size. In her study, two of 198 pregnant women with a deployed air bag and two of 622 pregnant women without air bags experienced fetal death.

“We need studies with more women and a larger population of women in crashes across the country or in other countries to really determine what those numbers mean,” she said.

“One of the main messages beyond air bags is that pregnant women are best protected by wearing a seatbelt in motor vehicles,” said Schiff. “It’s going to protect you and your baby. Prior studies in non-pregnant populations have shown that air bags do not add substantial additional protection if you are wearing a seat belt.”

This study included investigators at Group Health Research Institute in Seattle. The project was supported by a grant from the Centers for Disease Control and Prevention.