The current recommendation for prenatal vitamin D supplementation is 400 IU to 600 IU per day. But could higher doses be any better for the child of a pregnancy? In a randomized trial, higher doses of vitamin D supplementation was analyzed as part of a study in Denmark involving 623 women and their offspring (584 children). They examined the effects of 2,500 IU vitamin D per day in addition to the standard 400 IU per day, compared to placebo, from 24 weeks gestation to 1 week postpartum.
The growth parameters of the children were evaluated at ages 3 and 6 years. At 6 years, children whose mothers received the sevenfold higher vitamin D supplementation had greater whole body bone mineral content, greater total body less the head bone mineral content and greater head bone mineral density compared with the children of mothers who received the standard 400 IU daily. The actual visual size of the head was no different between the groups.
Commentary: The best most appropriate dose of vitamin D to supplement for pregnant women is still under debate. It is important to realize, children with a vitamin D deficiency manifested as severe as rickets, do have something called, craniotabes. Craniotabes is a softening or thinning of the skull in infants and children, although can be normally present in newborns. But in this condition it is seen mostly in the occipital region (back part of head) and in the parietal bones (side part above the ears). These bones are then too soft and with pressure, can collapse.
In the current study, vitamin D supplementation influenced bone mineralization most significantly in the winter and spring, which is when deficiencies are most common. It was also observed that in those whose mothers were initially deficient, this seasonal influence had the most marked effect.
Vitamin D supplementation is a simple, safe, inexpensive strategy which could have meaningful effects for infants and children at high risk for vitamin D deficiency. These folks include darker skinned individuals, those who are overweight, those who live at high altitudes, and those who do not get enough daylight outdoor time.
I see no reason why 2,500-3,000 daily amount of vitamin D would be unsafe for pregnant women, although more research is needed to determine all the benefits and put into routine practice.
Reference: Brustad N, et al. Effect of high dose vs standard dose vitamin D supplementation in pregnancy on bone mineralization in offspring until age 6 years: A prespecified secondary analysis of a double-blinded, randomized clinical trial. JAMA Pediatr 2020 Feb 24 (E-pub)
