Cerebral palsy risk increased among children conceived in winter and spring


In a recent study, the risk of cerebral palsy was slightly increased among children conceived in the winter and spring compared to summer.

Cerebral palsy risk increased among children conceived in winter and spring: © PhotoSeka - stock.adobe.com

Cerebral palsy risk increased among children conceived in winter and spring: © PhotoSeka - stock.adobe.com

According to a recent published in JAMA Network Open, children conceived in the winter and spring experience a slight increase in cerebral palsy (CP) risk.

CP is the most common neuromotor and physical disability in children, with 2 to 3 per 1000 live births impacted in the United States. Currently, there is little data on the etiological causes of CP. However, investigating seasonal patterns of the condition may provide further understanding on how seasonally varying environmental risk factors impact disease risk.


  • Seasonal Influence on Cerebral Palsy (CP) Risk: Children conceived during the winter and spring seasons are found to have a slightly higher risk of developing cerebral palsy, a common neuromotor and physical disability in children.
  • Lack of CP Etiological Data: There is limited information regarding the causes of cerebral palsy, making it important to explore potential environmental risk factors, such as seasonal patterns, that may contribute to the condition.
  • Large California Cohort Study: The study analyzed a cohort of 4,652,013 live births in California between 2007 and 2015 to investigate how the season of conception affects CP risk.
  • Increased CP Risk in Winter and Spring: The research revealed that CP risk was approximately 9% to 10% higher in children conceived during the fall or winter months compared to those conceived in the summer. Specifically, January, February, or May conception had a 15% greater risk than July conception.
  • Social and Environmental Factors: The association between seasonal conception and CP risk was stronger among children born to mothers living in high-risk neighborhoods, racial and ethnic minorities, and mothers with lower education levels. This suggests that social and environmental factors may interact with seasonal effects in influencing CP risk, prompting the need for further research in this area.

Investigators conducted a cohort study in California to bridge the information gap about how season of conception impacts CP risk. The study cohort included 4,652,013 live births which occurred in California between 2007 and 2015.

Excluded birth records included records missing maternal residential address or last menstrual period information and records with potential cofounding errors. There were 4,468,109 live births included in the final analysis, of which 4697 children had CP.

CP was defined by study authors as, “a group of nonprogressive lesions or disorders in the brain that are characterized by paralysis, spasticity, or abnormal movement and/or posture control that manifested in early childhood.”Cofounders were determined by extracting maternal and child sociodemographic data.

Conception data was estimated using the child’s date of birth and length of gestation based on the last menstrual period. Winter was defined as January to March, spring as April to June, summer as July to September, and fall as October to December.

Of participants, 51.2% were male, 28.3% had a maternal age of 19 to 25 years and 27.5% of 26 to 30 years, 5.6% were Black, 13.5% Asian, 49.8% Hispanic, and 28.3% non-Hispanic White. CP was seen more often in children born to older, obese, Black, and Hispanic mothers, as well as mothers with a lower education level or who smoked during pregnancy.

The risk of CP was estimated as 9% to 10% higher among children conceived in the fall or winter compared to those conceived in the summer. When evaluating specific months, the risk of CP was 15% greater for children conceived in January, February, or May, than those conceived in July.

These associations were strengthened among children born to mothers living in high-risk neighborhoods based on sociodemographic factors. Racial and ethnic minority status and lower maternal education also strengthened these associations.

These results indicated an increased risk of CP among children conceived in the winter or spring seasons compared to the summer season. Investigators recommended future etiological research on CP to evaluate exposure effects from seasonally varying environmental risk factors.


Zhuo H, Ritz B, Warren JL, Liew Z. Season of conception and risk of cerebral palsy. JAMA Netw Open. 2023;6(9):e2335164. doi:10.1001/jamanetworkopen.2023.35164

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