A pregnant woman who wears a seat belt greatly reduces the risk that her baby will die or be seriously hurt in a vehicle crash, according to a study that debunks the notion that seat belts are harmful to the fetus.
The University of Michigan researchers estimated that based on their findings, published on Wednesday, the lives of 200 of the roughly 370 fetuses killed yearly in U.S. vehicle crashes would be spared if all pregnant women wore seat belts.
"Seat belts absolutely protect the fetus -- and not wearing a belt is a big problem," Dr. Mark Pearlman, who led the study, said in a telephone interview. "Every single time they get in a motor vehicle, pregnant women should wear their seat belts without question -- every single time."
The researchers performed detailed analyses of 57 crashes involving women who were at least 20 weeks pregnant. Twelve fetuses were killed in the crashes.
Pregnant women who wore seat belts cut the risk of their fetus being killed or experiencing other serious complications in a vehicle crash by 84 percent compared to women who did not wear seat belts, the researchers said.
In the study, 72 percent of the women were wearing seat belts. Only 38 percent of the women whose babies died or suffered serious complications were wearing seat belts.
The serious non-fatal complications included the woman's placenta prematurely separating from the uterine wall, preterm birth prior to 32 weeks of pregnancy and direct fetal injury, the researchers reported in the American Journal of Obstetrics & Gynecology.
Pearlman said he hoped the findings dispel once and for all what he called the "myth" that wearing a seat belt is harmful for the fetus
"What this study also shows is that if you are unbelted, the mom did a lot worse. And since the baby's dependent upon the mom entirely for everything, that's part of what's going on here -- you're protecting the mom, you're also protecting the baby," Pearlman said.
Pearlman offered some tips on the proper way for pregnant women to wear seat belts.
He said the lap strap should be placed under the belly as much as possible, across the hips. The shoulder strap should be placed between the breasts and to the side of the belly. Seat belt straps should not go directly across the stomach and should be below the belly button as low they can comfortably go. And the seat belt should be snug, not loose.
Overall, about 82 percent of people in the United States wear seat belts regularly, Pearlman said. The researchers said 6 percent to 7 percent of pregnant women are involved in some type of car crash during their pregnancy.
The study also turned up no evidence that air bags were harmful to fetuses, and Pearlman said he does not recommend disabling them.