Potential Dangers When You're "Driving for Two"

Pregnancy while driving may increase risk of motor vehicle crash

/ Author:  / Reviewed by: Robert Carlson, M.D Beth Bolt, RPh

(RxWiki News) A woman experiences a variety of changes to her body while she's pregnant. While these are normal changes, they might influence her alertness or the way she's feeling occasionally.

If any person is feeling tired, nauseated or otherwise not well, it may increase their risk of an accident while driving.

A recent study found that pregnant women who may feel fatigue or nausea more often than usual had a higher risk of a car accident while driving in their second trimester, compared to their risk while not pregnant.

Their risk of a car accident was lowest in the third trimester, and it was about the same in the first trimester as when they were not pregnant.

"Be alert and follow traffic laws while driving."

The study, led by Donald Redelmeier, MD, of the Department of Medicine at the University of Toronto, looked at whether the risks of a crash while driving were higher when a driver was pregnant.

The researchers analyzed the driving records of 507,262 women who gave birth at least once between April 2006 and March 2011.

Only women over age 18 with a valid driver's license and car insurance were included. Women under the care of a midwife were also not included.

During the time period of the study, the women were involved in 6,922 motor vehicle crashes in the three years before they became pregnant, for a rate of 177 crashes per month.

While in their second trimester of pregnancy, however, the crashes these women were involved in occurred at a rate of 252 crashes per month, for a total of 757 during the study time period.

Therefore, car accidents occurred 42 percent more often during women's second trimester than when they were not pregnant.

However, this increased risk is very small compared to the increased risk related to other behaviors while driving. For example, using a cell phone while driving increases the risk of a crash by 400 percent.

The second trimester included a higher rate of crashes than the first or third trimesters.

The rate of crashes during the first trimester was about 4.3 crashes per 1,000 women each year, about the same as the rate during the three years before pregnancy, which was 4.6 crashes per 1,000 women a year.

The second trimester, the rate was 7.7 crashes per 1,000 women each year, but during the third trimester, the rate was only 2.7 crashes per 1,000 women each year.

In the year after the women gave birth, the rate was 2.4 crashes per 1,000 women each year.

The increased risk existed despite differences among the women's demographics, differences among the characteristics of the car accidents and any differences regarding the women's pregnancy characteristics.

The researchers also looked at other types of accidents but did not see an increase in accidental falls, pedestrian accidents or car crashes as a passenger for these women while they were pregnant.

The women also did not have higher rates while pregnant of intentional injury or risky behaviors, compared to when they were not pregnant.

Several changes in the body that occur during pregnancy might lead to fatigue, nausea, accidentally getting distracted and sleeping problems.

The researchers suggested that some of these factors might play a role in the increased risk of a car crash during pregnancy.

"Fatigue is more common during pregnancy," said Andre Hall, MD, an OBGYN at Birth and Women's Care, PA in Fayetteville, NC. "As a result pregnant women must pay close attention to tasks that require coordination and higher order thinking."

He said reaction times can also be delayed, something potentially related to functional anemia in pregnancy, which relates to changes in blood volume.

"This may also be related to the hormonal changes common during pregnancy," Dr. Hall said. "However, armed with knowledge, pregnant women generally have no difficulty maneuvering the daily tasks of living."

The authors noted some of the ways that women can reduce their risk of a car crash.

"Motor vehicle crashes can be prevented with basic safety practices such as avoiding excessive speed, minimizing distractions, signaling turns, obeying stop signs, and always using a seatbelt," they wrote.

The study was published May 12 in the Canadian Medical Association Journal. The authors reported no conflicts of interest.

The research was funded by a Canadian Institutes of Health Research, the Determinants of Community Health course at the University of Toronto and the D+H SRI Summer Student Research Program.

Review Date: 
May 11, 2014
Last Updated:
May 26, 2014