In utero exposure to extra vitamin D from food fortification and the risk of subsequent development of gestational diabetes: the D-tect study.
BACKGROUND
The primary aim of this study was to assess whether exposure during fetal life to extra vitamin D from food fortification was associated with a reduction in the risk of subsequently developing gestational diabetes mellitus (GDM). Furthermore, we examined whether the effect of the vitamin D from fortification differed by women's season of birth.


METHODS
This semi-ecological study is based on the cancellation in 1985 of the mandatory policy to fortify margarine with vitamin D in Denmark, with inclusion of entire national adjacent birth cohorts either exposed or unexposed to extra vitamin D in utero. The identification of GDM cases later in life among both exposure groups was based on the Danish national health registers. Logistic regression analyses generating odds ratios (ORs) and 95% confidence intervals (95% CIs) were performed.


RESULTS
Women who were prenatally exposed to the extra vitamin D from fortification tended to have a lower risk of subsequently developing GDM than unexposed women (OR 0.87, 95%CI 0.74,1.02, P = 0.08). When analyses were stratified by women's season of birth, exposed women born in spring had a lower risk of developing GDM compared to unexposed subjects (OR 0.68, 95%CI 0.50,0.94, p = 0.02).


CONCLUSION
This study suggests that prenatal exposure to extra vitamin D from mandatory fortification may lower the risk of developing gestational diabetes among spring-born women.


TRIAL REGISTRATION
This study is part of the D-tect project, which is registered on clinicaltrials.gov: NCT03330301 .
['Keller|Amélie|A|0000-0003-1404-6715', 'Stougård|Maria|M|', 'Frederiksen|Peder|P|', 'Thorsteinsdottir|Fanney|F|', 'Vaag|Allan|A|', 'Damm|Peter|P|', 'Jacobsen|Ramune|R|', 'L Heitmann|Berit|B|']
D000328:Adult D003718:Denmark D016640:Diabetes, Gestational D005260:Female D005527:Food, Fortified D006801:Humans D039382:Maternal Nutritional Physiological Phenomena D011247:Pregnancy D011297:Prenatal Exposure Delayed Effects D012306:Risk D012621:Seasons D014807:Vitamin D D014815:Vitamins D055815:Young Adult
Vitamin D Gestational diabetes mellitus Fetal programming Food intake Public health epidemiology