Insufficient vitamin D supplement use during pregnancy and early childhood: a risk factor for positional skull deformation.

Vitamin D insufficiency during pregnancy is associated with disturbed skeletal homeostasis during infancy. Our aim was to investigate the influence of adherence to recommendations for vitamin D supplement intake of 10 μg per day (400 IU) during pregnancy (mother) and in the first months of life (child) on the occurrence of positional skull deformation of the child at the age of 2 to 4 months. In an observational case-control study, two hundred seventy-five 2- to 4-month-old cases with positional skull deformation were compared with 548 matched controls. A questionnaire was used to gather information on background characteristics and vitamin D intake (food, time spent outdoors and supplements). In a multiple variable logistic regression analysis, insufficient vitamin D supplement intake of women during the last trimester of pregnancy [adjusted odds ratio (aOR) 1.86, 95% (CI) 1.27-2.70] and of children during early infancy (aOR 7.15, 95% CI 3.77-13.54) were independently associated with an increased risk of skull deformation during infancy. These associations were evident after adjustment for the associations with skull deformation that were present with younger maternal age and lower maternal education, shorter pregnancy duration, assisted vaginal delivery, male gender and milk formula consumption after birth. Our findings suggest that non-adherence to recommendations for vitamin D supplement use by pregnant women and infants are associated with a higher risk of positional skull deformation in infants at 2 to 4 months of age. Our study provides an early infant life example of the importance of adequate vitamin D intake during pregnancy and infancy.