Does Season of Conception Affect Cerebral Palsy Risk in Children?

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Article from Jessica Nye PhD via Neuro Advisor.

The prevalence of cerebral palsy (CP) is slightly higher among babies conceived during the winter and spring months than the summer months, according to study findings published in JAMA Network Open.

The most common neuromotor and physical disability, CP, affects 2 to 3 children per 1000 live births in the United States. As the aetiology of CP is not fully understood, the researchers designed this study to evaluate whether seasonal patterns affect its prevalence.

The researchers from Yale University sourced data for this study from the California Department of Developmental Services. Births (N=4,468,109) that occurred statewide between 2007 and 2015 and evaluated for CP on the basis of conception season and month. cerebral palsy was defined as nonprogressive lesions or disorders in the brain causing paralysis, spasticity, abnormal movement, and/or abnormal posture control manifesting in early childhood.

Most of the children were:

• boys (51.2%),
• 49.8% were Hispanic,
• 28.3% were White,
• 13.5% were Asian,
• 5.6% were Black,
• 28.3% were born to a mother aged 19 to 25, and
• 27.5% to a mother aged 26 to 30.

Children conceived during winter (relative risk [RR], 1.09; 95% CI, 1.01-1.19) or spring (RR, 1.10; 95% CI, 1.02-1.20) were more likely to have CP than children conceived in summer.

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Stratified by month of conception, compared with July, CP was more likely among children conceived in January (RR, 1.15; 95% CI, 1.01-1.32), February (RR, 1.15; 95% CI, 1.01-1.33), and May (RR, 1.15; 95% CI, 1.01-1.33).

These trends were stronger among mothers who resided in neighbourhoods with high socioeconomic vulnerability (winter: RR, 1.17; spring: RR, 1.24) and with high racial or ethnic minority status (winter: RR, 1.18; spring: RR, 1.23).

Stratified by subtype of CP, these trends were significant for spastic CP (winter: RR, 1.16; spring: RR, 1.18), specifically bilateral, spastic CP (winter: RR, 1.17; spring: RR, 1.17), but not for ataxic, dyskinetic, unilateral spastic, or another subtype CP.

A significant indirect effect of Apgar score at 5 minutes was observed for spring conceptions (10.4%) but not for winter conceptions (0.8%).

These findings could have been biased, as mild cases of CP may have been overlooked.

These data indicated that seasonality may affect CP prevalence. The researchers concluded, “To our knowledge, this was the largest cohort study to date to suggest that seasonally varying factors may contribute to CP occurrence, and the strength of observed associations may also be affected by social vulnerability. While the results should not be used to promote a change in family planning, our findings suggested that future etiological research on CP should investigate the exposure effects from seasonally varying environmental risk factors.”

References:

Zhuo H, Ritz B, Warren JL, Liew Z. Season of conception and risk of cerebral palsy. JAMA Netw Open. Published online September 22, 2023. doi:10.1001/jamanetworkopen.2023.35164