Traffic crash during pregnancy increases cerebral palsy risk to unborn child

Being in a motor vehicle crash during pregnancy nearly doubles the woman's risk that her unborn child will be subsequently diagnosed with cerebral palsy by the age of three, according to a new study from the Institute for Clinical Evaluative Sciences (ICES).

“Our data suggest a traffic crash in pregnancy can lead to an increased risk of cerebral palsy in infancy for cases when the woman subsequently had preterm labour. No increased risk was apparent for cases followed by a term delivery,” says the study’s lead author Dr. Donald Redelmeier, who is a scientist at ICES, a staff physician at Sunnybrook Health Sciences Centre and a professor at the University of Toronto’s Institute of Health Policy, Management and Evaluation..

However, the absolute risks are still modest for those who delivered preterm. Taking into account all other risks, the absolute risk of cerebral palsy following a preterm pregnancy is 7.3 per 1,000 if no traffic crash occurs and 18.2 per 1,000 if a traffic crash does occur. “Cerebral palsy is a rare outcome,” says study co-author Dr. Jon Barrett who is a professor of obstetrics at the University of Toronto.

The researchers identified every woman in Ontario who gave birth to a newborn between 2002 and 2012 and then followed each baby for three years examining early childhood outcomes. This amounted to 1,325,660 newborns, of whom 7,933 (about 1 in 150) had been in a significant motor vehicle crash during pregnancy and 2,328 (about 1 in 600) were subsequently diagnosed with cerebral palsy.

The study was published today in the journal BMJ Open.

Cerebral palsy is a term used to describe a group of conditions interfering with body movement, muscle coordination, and other aspects of neurological function. It is caused by damage to one or more specific areas of the brain during fetal development, around the time of birth, or the early years of infancy. Cerebral palsy is incurable yet therapy can help lessen further complications. 

About 1 in 50 pregnant women were involved in a traffic incident at some point during the nine months before delivery. The middle months of pregnancy accounted for a disproportionate amount of risk and more than half of the crashes happened in the afternoon. Less than one per cent of women delivered within 48 hours of the crash but about seven per cent of women delivered preterm after a traffic crash.

The researchers suggest two reasons why a motor vehicle crash may harm a fetus:

• The sudden impact and deceleration is like a concussion and can directly damage brain tissue
• Blunt forces damage the placenta and deprive the fetus of nutrients needed for development

“A motor vehicle crash is not unique to pregnancy but the stakes are substantially higher for the unborn child. Pregnant women should be reminded to drive carefully. The standard advice includes avoiding excess speed, signaling turns, yielding right-of-way, obeying stop signs, minimizing distractions, and always using a seatbelt. That's good advice for the rest of us too who share the road and want to avoid colliding with a pregnant driver,” says Redelmeier.

“Motor vehicle crashes during pregnancy and cerebral palsy during infancy: a longitudinal cohort analysis” was published today in the journal BMJ Open.

Author block: Donald A Redelmeier, Faisal Naqib, Deva Thiruchelvam and Jon F Barrett.

The Institute for Clinical Evaluative Sciences (ICES) is an independent, non-profit organization that uses population-based health information to produce knowledge on a broad range of healthcare issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting healthcare needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy. For the latest ICES news, follow us on Twitter: @ICESOntario

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