Buckle Up Baby

Many mothers have thought twice when tightening a seat belt over their baby bumps. Not only can it be uncomfortable for very pregnant women to buckle up, they may wonder whether the strap could hurt the fetus if pulled taut across the belly in an accident. A new study by researchers at the University of Michigan found good reason for moms to stop fretting and strap themselves in: about 200 fetuses each year would not be lost if pregnant women properly buckled their seat belts every time they were in an automobile, no matter which seat they're in.

The study, which appears in the latest issue of the American Journal of Obstetrics & Gynecology, debunks a common myth—that wearing a tight seat belt in an accident can harm a fetus—that seems to persist despite doctors' best efforts, according to Dr. Mark Pearlman, the lead study author and vice chair of the department of obstetrics and gynecology at the University of Michigan Health System.

"Patients worry because the belt goes right across their belly. But the belt prevents a woman from being thrown into the steering wheel or the dashboard, which really protects her," says Pearlman, who estimates that 369 fetuses are killed in car accidents each year, which is more than the number of newborns killed in car accidents during their first year of life.

"If you put your hand across your lower abdomen, where the lap belt sits, you'll notice that it really loads on the pelvic bone itself," he adds. "So in a crash it will intrude on the uterus a little, but then it will stop, because the pelvic bone will stop everything from moving forward further. If she's not wearing that belt, she'll be thrown into the steering wheel, and all the energy in that crash is loaded right into a place that's much more dangerous."

The researchers concluded that at a crash speed of 20 mph (a standard high-severity crash) the risk for fetal death or major complications was approximately 12 percent when the mother was wearing a seat belt properly, compared with 70 percent when she was not properly restrained. Further, they found that across all crash severities, from 1 mph to 40 mph, wearing seat belts would likely save about 84 percent of babies.

Using funding from General Motors and the Alliance of Automobile Manufacturers, Pearlman teamed up with engineers and doctors to perform detailed analyses on 57 severe automobile crashes involving pregnant women. The group sent investigative teams out to crash sites to measure the severity of the accidents by looking at factors such as damage to the car and airbag deployment. This allowed them to control for crash severity and isolate seat belt use as their main variable. Pearlman concedes that the sample size may seem small, but the study is the largest of its kind, and the results offer ample evidence that seat belts can be a factor in saving fetuses in crashes.

"One of the interesting things we found in this study is that, of those who had bad outcomes [including miscarriage or preterm labor], 62 percent of the women were not wearing their seat belts," he says. "So a lot more women who ended up with bad outcomes weren't wearing their seat belts."

Eighty-two percent of adults in the United States wear their seat belts regularly, and only 72 percent of the women in the Michigan study did. Though the sample size makes it difficult to draw definitive conclusions, the numbers do suggest that pregnant women, whether out of discomfort or concerns about the safety of their unborn children, may be wearing their seat belts less frequently than the population at large.

That's why researchers say the most important recommendation they have for pregnant women is to wear a seat belt at all—that, they say, matters much more than wearing it a certain way. For maximum safety, the lap belt should be put on below the belly button so it fits below the bump, while the shoulder harness should be worn off to the side of the belly, between the breasts and over the middle of the collarbone. For women who find that a normal seat belt no longer fits around their bellies, researchers suggest seat belt extenders. In addition, they say, airbags should never be turned off, because they are aimed higher (at the chest and face) and also help to keep drivers and passengers from hitting the steering wheel or dashboard in an accident.

"The greatest thing about this is that it doesn't cost anything," Pearlman says. "Think about saving 200 babies—we're probably talking millions if not tens of millions of dollars [to do that] in a hospital. But you don't even have to buy a seat belt. All you have to do is help spread the word that women who are pregnant and in a vehicle should buckle up every single time."