Maternal unintentional injury during pregnancy associated with higher risk of cerebral palsy

by Molly Munsell, Vincent So, Alex Gipsman, MD

Originally published by 2 Minute Medicine® (view original article). Reused on AccessMedicine with permission.

1. Based on a large cohort study, children born to mothers who had an unintentional injury during pregnancy had a 33% increased risk of cerebral palsy (CP) diagnosis.

2. More severe maternal injuries were associated with greater increases in CP risk.

Evidence Rating Level: 2 (Good)

Study Rundown:

Cerebral palsy (CP) is a broad category of movement disorders and a common cause of physical disability. Known risk factors include preterm birth, complicated delivery, and birth asphyxia of various etiologies. This population study aimed to explore any effect on CP risk associated with maternal unintentional injury, including motor vehicle accidents and falls. In a cohort of more than 2 million children with a mean follow-up time of 8 years, 3.9% were exposed to maternal unintentional injury in utero. The overall prevalence of CP diagnosed at or after birth was 0.3%. For children exposed to maternal unintentional injury, the mean incidence rate for CP was 4.36 per 10,000 child years, compared to 2.93 per 10,000 in the non-exposed group. Maternal injury was associated with an adjusted 33% higher risk of CP. Maternal injuries severe enough to require hospitalization and delivery within one week of injury were associated with a higher adjusted hazard ratio of 3.40. This very large cohort study provides compelling evidence linking maternal injury and offspring cerebral palsy. In the case of severe injuries either precipitating or requiring immediate delivery, this link may intuitively be related to complications such as preterm labor, placental abruption, or uterine rupture. For milder injuries, the causative pathway for elevated CP risk is less clear and necessitates further study. Though the risk of unintentional injury during pregnancy of course cannot be eliminated, this association represents another reason to mitigate it as much as possible.

In-Depth [retrospective cohort]:

Live births of infants at more than 20 weeks gestation in hospitals in Ontario, Canada between 2002 and 2017 were included. Mothers’ and infants’ charts were linked within the database; children’s records through 2018 were examined. CP diagnosis was determined based on either two or more outpatient diagnostic codes at least two weeks apart or a single inpatient diagnosis of CP between birth and age 16. A total of 5,317 children within the cohort had CP, of whom 292 had been exposed to maternal unintentional injury. The hazard ratio of 1.33 was adjusted for maternal age, parity, eligibility for drug benefits based on financial need, the start of prenatal care, rural residence, and neighborhood socioeconomic index, and had a 95% confidence interval (CI) of 1.18-1.50. The adjusted hazard ratio for a severe maternal injury requiring hospitalization and delivery was 3.40 with a 95% CI of 1.93-6.00. Cox proportional hazard models adjusted for birth year did not vary significantly. Quantitative analyses for bias based on CP misclassification and unmeasured maternal socioeconomic and other factors were also reported.

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