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A large Swedish study found that higher maternal BMI during early pregnancy is linked to a meaningfully greater risk of multiple sclerosis in children. Compared to normal-weight mothers, obese mothers had a 35% higher rate of MS in offspring, while overweight mothers had a 20% higher rate. Researchers believe a pro-inflammatory intrauterine environment and lower vitamin D levels may help explain the connection.
A nationwide Swedish cohort study of over 1.5 million births has found that higher maternal BMI in early pregnancy is associated with a significantly increased risk of multiple sclerosis (MS) in offspring — adding to growing evidence that MS susceptibility may begin before birth.
The study, presented at the ECTRIMS-ACTRIMS 2026 conference, tracked births from 1992 to 2007 with follow-up through 2025. Of the 1.5 million births, 1,539 offspring were later diagnosed with MS. Researchers found that maternal obesity raised the rate of offspring MS by 35%, and overweight by 20%, compared to normal weight. Each additional BMI unit was tied to a 3% higher MS hazard — with similar patterns seen for both pediatric- and adult-onset disease.
Researchers suggest a pro-inflammatory intrauterine environment and lower vitamin D levels — both linked to excess weight — may be driving the association. However, shared genetics and residual confounding remain possible explanations.
By the Numbers:
Why it matters: These findings suggest that prenatal factors — including maternal weight — may play a role in shaping a child's long-term neurological risk, opening potential avenues for early intervention and preconception counseling.
