Shifting the focus from infants and children in safety seats, researchers and car manufacturers are looking to prevent fetal deaths by making automobile travel safer for expectant mothers.

Biomedical researchers are working with automakers to develop a computer-aided model of pregnant drivers and passengers so they can develop better crash-protection features in future vehicle designs.

Stefan Duma, head of the Virginia Tech-Wake Forest University School of Biomedical Engineering and Sciences in Blacksburg, Va., said the school recently completed a three-year research project, partly funded by Ford, to gather data about the tissue composition and dimensions of pregnant women and their fetuses.

"We can develop restraint systems for any vehicle and any occupant, but we first have to see the injuries themselves, what happens to the placenta and uterus tissues during an accident," said Duma, who has done research for a range of applications, including safety features for Blackhawk military helicopters.

There are no official federal statistics kept on the number of fetal deaths in car accidents. But Duma says different groups estimate 300 to several thousand such deaths occur annually as a result of vehicle crashes _ about four times the number of victims between infancy and 4 years old.

Overall, about 27,000 vehicle occupants died in car crashes in 2008, according to the National Highway Traffic Safety Administration, and auto accidents are the single largest cause of death for pregnant women.

Dr. Melissa Schiff, an obstetrician and epidemiologist at the University of Washington's Harborview Injury Prevention and Research Center, welcomes the attention to pregnant women.

"We really do need to get more information and to design vehicles better for this special population," said Schiff, who has done several studies on motor-vehicle crashes and pregnancy. "It just really flies under the radar _ people focus so much on infants and booster seats."

Researchers used data from computerized tomography, or CT, scans taken at Wake Forest's hospital to determine the dimensions of a fetus, uterus and placenta at 30 weeks' gestation. They also tested varying forces' effects on actual uterine and placental tissue samples so they could devise a more accurate simulation of how crashes affect women and their fetuses.

Ford safety researcher Stephen Rouhana says the data gathered during the project ultimately will be used to improve safety features in the company's vehicles. Rouhana and his team have worked with a variety of crash-test dummies but they want to determine what happens inside a pregnant woman's body during different accident scenarios.