Southampton, UK—Supplementing with vitamin D during pregnancy appears to substantially reduce the risk of infants having atopic eczema, according to a new study.

The report in the British Journal of Dermatology found that the lowered risk occurred if expectant mothers took 1,000 international units (IU) of vitamin D daily from when they were 14 weeks pregnant until they delivered. The University of Southampton researchers advised that the effect was especially strong in babies who were later breastfed for more than 1 month.

Background information in the study notes that one in six children aged one to five has atopic eczema, and cases have risen globally over the last decades.

The research at the University of Southampton Medical Research Council Lifecourse Epidemiology Centre and the NIHR Southampton Biomedical Research Centre is touted as the first randomized, controlled trial to show evidence of reduced risk of atopic eczema in infants of mothers who took vitamin D supplements during pregnancy.

The trial included more than 700 pregnant women—352 received the supplements from 14 weeks until they gave birth and 351 took a placebo. The eczema research was part of the UK Maternal Vitamin D Osteoporosis Study (MAVIDOS).

"Our aim was to see whether taking 1,000 IU of vitamin D (cholecalciferol) as a supplement during pregnancy would decrease the risk of atopic eczema in babies. We also wanted to establish whether breastfeeding had any effect on this," stated first author Sarah El-Heis, MBBS, MRCP, DM. "Our results showed that babies of mothers who received supplements had a lower chance of having atopic eczema at 12 months, which supports recommendations for Vitamin D supplements to be routine during pregnancy. We found no effect at 24 and 48 months suggesting that other postnatal influences might become more important beyond infancy or that the babies themselves might also need to be supplemented during the postnatal period for a sustained effect."

Adjusting for breastfeeding duration, the results indicated that babies of women who received 1,000 IU cholecalciferol daily had a lower odds ratio (OR) of atopic eczema at age 12 months (OR [95% CI] 0.55 [0.32-0.97], P = .04). The researchers pointed out that the effect weakened and was not statistically significant at ages 24 and 48 months (OR 0.76 [0.47-1.23] and 0.75 [0.37-1.52], respectively).

In addition, the researchers noted, "The statistical interaction of intervention and breastfeeding duration in relation to eczema at age 12 months was not significant (P = .41), but stratification showed a reduced infantile eczema risk in intervention group infants breastfed for >1 month (OR 0.48 [0.24,0.94], P =.03) and not in those breastfed for <1 month (OR 0.80 [0.29,2.17], P = .66)."

Lead researcher Keith Godfrey, BM, FRCP, PhD, explained why he and his colleagues embarked on the study. "We know that Vitamin D can affect the immune system and the proteins that make up our skin," he stated. "We were interested to know if Vitamin D supplements taken by pregnant women would have an impact on their child's risk of atopic eczema. Our findings showed a positive effect, which was more evident in infants that breastfed. This may reflect supplementation during pregnancy [from] increasing the amount of Vitamin D in breast milk."

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