You might think strapping a tight seat belt over a growing pregnant belly can harm an unborn baby. But not buckling up is what harms fetuses, says a newly-released University of Michigan study concluding that pregnant women who wear seat belts significantly reduce the risk that their babies will die or be seriously hurt in a vehicle crash.

Study findings, published on Wednesday, reveal that the lives of 200 of the roughly 370 fetuses killed each year 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," says study lead Dr. Mark Pearlman. "Every single time they get in a motor vehicle, pregnant women should wear their seat belts without question -- every single time."

It's simple: Seat belts protect moms. And they protect babies, says Pearlman who offers these tips for proper pregnant buckling.

• 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, to the side of the belly.
  
  

• Seat belt straps should not go directly across the stomach but should be below the belly button as low they can comfortably go.
  
  

• The seat belt should be snug, not loose.
  
  

Pearlman's study also showed no evidence that air bags are harmful to fetuses. He therefore does not recommend disabling them.