Higher Maternal BMI Linked to Offspring MS Risk, Research Says
Higher body mass index in early pregnancy is linked to an elevated multiple sclerosis rate in offspring, according to observational research presented on October 21, 2026, at the 10th Joint European Committee for Treatment and Research in Multiple Sclerosis-Americas Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS-ACTRIMS) congress, as reported by Medscape.
- Maternal obesity during early pregnancy is associated with a 35% higher rate of multiple sclerosis in offspring compared to normal weight.
- Maternal overweight shows a 20% higher rate of offspring multiple sclerosis in the Swedish population-based cohort study.
- Absolute incidence remains low across all evaluated body mass index groups, ranging from 0.37 to 0.45 per 10,000 person-years.
Cohort Study of 1.5 Million Swedish Births Links Early Pregnancy Weight to Offspring Neurologic Disease
The nationwide observational study examined more than 1.5 million singleton births recorded in Sweden between 1992 and 2007, with follow-up tracking through the end of 2025 via national registers. Researchers categorized maternal body mass index from measurements taken at the first antenatal visit, which occurred at a median gestation of 10 weeks. This early timing reflects the first antenatal visit, as noted by study investigator Kyla Anne McKay, PhD, assistant professor of neuroepidemiology at Karolinska Institutet in Stockholm, Sweden, in her interview with Medscape Medical News.
Among the 1,524,863 births analyzed, investigators identified 1,539 offspring subsequently diagnosed with multiple sclerosis through Sweden’s National Patient Register, requiring at least three diagnostic codes recorded on separate dates. Of those diagnosed, 69% were female. The absolute incidence per 100,000 person-years measured 0.37 in the underweight and normal weight categories, rising to 0.42 in the overweight group and 0.45 in the obesity group.
Statistical Adjustments and Hazard Ratios Across Weight Categories
To isolate the association between maternal weight and offspring outcomes, the statistical models adjusted for maternal age, parity, region of birth, education level, cohabitation with a partner, height, smoking status, multiple sclerosis history, and year of delivery. Compared to offspring of mothers with normal weight, those born to mothers with overweight exhibited an adjusted hazard ratio of 1.20, while offspring of mothers with obesity showed an adjusted hazard ratio of 1.35. Each single-unit increase in maternal body mass index corresponded to a 3% higher hazard of offspring multiple sclerosis overall, a 4% higher rate for pediatric-onset disease, and a 3% higher rate for adult-onset disease.
Emmanuelle L. Waubant noted that the findings contribute to understanding very early prenatal risk factors. However, Waubant cautioned that shared genetics could partly explain the associations. Additional limitations highlighted by investigators include the likelihood that children of mothers with elevated body mass index are more susceptible to high body mass index themselves—a known independent risk factor—as well as the potential for residual confounding and the fact that the oldest offspring were approximately 33 years old at the conclusion of follow-up.
Inflammatory Mechanisms and Biological Environment in Utero
The biological rationale connecting early pregnancy weight to offspring neurological outcomes involves systemic inflammation and metabolic factors. McKay stated that a proinflammatory intrauterine environment and low maternal vitamin D during gestation may help explain the observed risk increase.
Maternal body mass index in early pregnancy has been linked to autoimmune and neurologic outcomes in children. The Swedish Research Council funded the investigation.
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