Pregnancy and the Risk of Traffic Collision

Washington Monument at the National Mall in Washington, D.C. (Dr. Noorali Bharwani)
Washington Monument at the National Mall in Washington, D.C. (Dr. Noorali Bharwani)

The Canadian Medical Association Journal (CMAJ March 1, 2016) has awarded its top research honour to the authors of a study that showed women face an increased risk of serious car accidents during pregnancy.

Dr. Donald Redelmeier and his colleagues are the recipients of the Bruce Squires Award for their article “Pregnancy and the risk of a traffic crash,” which showed that pregnant drivers were 42 per cent more likely to have a serious collision that resulted in an emergency department visit. It generated the most public interest of any CMAJ research paper in 2015, says the CMAJ article.

Redelmeier’s team analyzed the health records of 507 262 Ontario women who gave birth between April 1, 2006 and March 31, 2011. The researchers found that the risk of a serious crash peaked in the fourth month of pregnancy, and was higher in the afternoon and in complicated traffic. It affected pregnant women regardless of their background, whether they had been pregnant before, or whether they were carrying a boy or a girl, says CMAJ article.

The authors concluded that pregnancy is associated with a substantial risk of a serious motor vehicle crash during the second trimester.

The World Health Organization classifies maternal deaths due to traffic crashes as coincidental and not related to the state of pregnancy. Others have argued that pregnancy is the root cause of such deaths, because pregnant women are more susceptible to crashes.

In 2014, CMAJ published a commentary (July 8, 2014) on Redelmeier’s research. The title of the commentary was “High risk of traffic crashes in pregnancy: Are there any explanations?” The commentary touched on several likely explanations. Here is the summary:

  1. Driving requires a high level of concentration and cognitive ability to maintain and complete a number of complex tasks. If there is any impairment in the driver’s cognitive ability, there may be an increased risk of a crash.
  2. The physiologic changes of pregnancy have been shown to increase fatigue and sleep deprivation in pregnant women.
  3. Prospective study using self-reported questionnaires showed that sleep length began to decrease during the second trimester and quality of sleep worsened during pregnancy.
  4. Maternal stress is also a common feature of pregnancy.
  5. Drivers who experience sleep deprivation, stress or fatigue will have an increased risk of a car crash.
  6. If busy urban areas are harder to navigate and require greater concentration in driving, then fatigue, tiredness and stress are likely to have a greater impact on the risk of a crash in urban areas.

There is no doubt studies have shown an increased risk of motor vehicle crashes among women in their second trimester of pregnancy.

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