Seasonal environment at birth may influence diabetes later.

Could the season and environment have an effect on infants being born? Study participants (9,737 youth with type 1 diabetes and 1,749 with type 2 diabetes) were identified by six collaborating U.S. centers.

Among the type 1 diabetic youths, percentage births decreased in October–February and increased in March–July. Similar patterns were observed when compared to race and gender. Geographic regions did seem to matter. There was a peak in study regions from the northern latitudes (Colorado, western Washington State, and southern Ohio) but no birth-month effect from more southern locations. Among type 2 diabetic youth, associations with birth month were inconclusive.

Conclusion
Spring births were associated with increased likelihood of type 1 diabetes but possibly not in all U.S. regions. Causal mechanisms may involve factors dependent on geographic latitude such as solar irradiance, but it is unknown whether they influence prenatal or early postnatal development.

Data suggests that environmental factors associated with birth in early winter in the U.S. may protect children and adolescents against type 1 diabetes. Factors related to spring birth, approximately during May in northern latitudes, may be associated with an increased diabetes incidence.

This mechanism may be enhanced when mothers and infants exercise less outdoors and wear more clothing that blocks sunlight. These mechanisms point to production of vitamin D. [Source: Diabetes Care]