Objective: To examine if fetal exposure to a small dosage of extra vitamin D from food fortification was associated with a decrease in the risk of pre-eclampsia later in life.
Design: Cancellation of the mandatory vitamin D fortification of margarine in 1985 created a societal experiment, with entire adjacent birth cohorts exposed or unexposed to extra vitamin D during fetal development. The Danish national medical health registries allowed the identification of pre-eclampsia cases later in life among all exposed and unexposed female individuals.
Setting: Denmark.
Subjects: Women born between June 1983 and August 1988, who gave birth to their first child at age 14·5-27·5 years (n 32 621).
Results: OR (95 % CI) for pre-eclampsia among women exposed v. unexposed to extra vitamin D from fortification during fetal development was 0·86 (0·76, 0·97). Exposure to extra vitamin D was associated with further reduced odds of pre-eclampsia (0·49 (0·34, 0·72)) among current smokers, but not among former smokers and non-smokers.
Conclusions: Additional vitamin D in fetal life from food fortification seems to reduce the risk of pre-eclampsia later in life. The risk reduction may be particularly strong among women who smoke during pregnancy.
Keywords: Fetal life; Fortification; Pre-eclampsia; Pregnancy; Vitamin D.