Pregnant women shouldn’t be afraid of harming their fetuses if they buckle up, say the authors of a University of Michigan Transportation Research Institute study of safety belt use during pregnancy. In fact, if every expectant mother were properly restrained an estimated half — or about 192 — of all reported pregnancy losses in crashes could be prevented each year.

Another finding is that airbags don’t “appear to worsen fetal outcomes” if mothers use lap/shoulder belts. This is important because some prior case studies have suggested that belts or a deploying airbag can harm a fetus during a crash. The Transportation Research Institute’s study suggests that “restraints protect the fetus by protecting the mother, because maternal injury is predictive of fetal outcome and proper restraint reduces maternal injury. Protecting the mother is the crucial factor for protecting the fetus.”

This study supports prior recommendations that pregnant women use safety belts. What’s different is that the new study looks at not only restraint use but also the severity of a range of crashes that included both positive and negative outcomes for the fetuses.

Researchers studied data from 57 real world front and side crashes involving pregnant women with fetuses of at least 20 weeks’ gestation. A dozen fetuses died, and 11 suffered major complications such as premature delivery and neonatal respiratory distress. Forty-one women were properly restrained, 6 improperly restrained, and 10 were unrestrained. None of the women used just a lap belt. The authors caution that the study excluded rollovers while including a more-than expected number of severe crashes, which are associated with pregnancy loss.

The fate of a fetus was strongly tied to how severe the crash was and how badly the mother was injured. The more severe a crash and/or a woman’s injuries, the more likely the fetus was to be seriously injured or killed.

For any given crash severity, fetuses of women who weren’t properly belted were more likely to be injured during the crash than those carried by women who were properly restrained. An estimated 62 percent of all fetal losses in motor vehicle crashes in the United States each year involve unbelted pregnant women. In the study, 8 of 10 unrestrained women had adverse fetal outcomes, including serious injury or fetal loss.

The National Highway Traffic Safety Administration advises pregnant women to position the lap belt low across the pelvis and below the belly, not on it. Shoulder belts should cross the chest and never be used behind the back or under an arm. Sitting at least 10 inches or more from the steering wheel or dashboard is recommended, especially as pregnancy progresses.

“Fetal outcome in motor-vehicle crashes: effects of crash characteristics and maternal restraint” by K.D. Klinich et al. is published in American Journal of Obstetrics & Gynecology (April 2008).

For more information - http://www.iihs.org/externaldata/srdata/docs/sr4307.pdf