Supplementation with vitamin D during pregnancy has no beneficial effect on asthma in the child, according to a Danish study published last night.
Dr Hans Bisgaard of the University of Copenhagen, Denmark and colleagues carried out a study of 623 women who took vitamin D3 (2,400 IU) or placebo every day from week 24 of pregnancy to a week after giving birth. Both groups also took 400 IU of vitamin D3 daily as part of usual pregnancy care.
When the child reached age three years of age, they were tested for persistent wheeze. Among the vitamin D3 group, 16% had been diagnosed with persistent wheeze, compared with 20% in the placebo group.
This result was statistically non-significant. Details appeared in The Journal of the American Medical Association yesterday (26 January). Despite the results, the authors believe that a clinically important protective effect of vitamin D3 supplementation cannot be excluded.
In a second study in the same journal, Dr Augusto Litonjua of Brigham and Women’s Hospital, Boston, USA and colleagues gave 881 pregnant women at high risk of having children with asthma either 4,000 IU vitamin D3 per day or placebo (again, both took the standard 400 IU of vitamin D3). The extra supplement was given at ten to 18 weeks’ gestation.
Among those in the supplement group, 24% developed recurrent wheeze by age three, compared with 30% in the placebo group. This was also not statistically significant.
The authors state: "Supplementation with 4,400 IU/d of vitamin D compared with 400 IU/d significantly increased vitamin D levels in the women. Longer follow-up of the children is ongoing to determine whether the difference is clinically important."
Chawes, B. L. et al. Effect of Vitamin D3 Supplementation During Pregnancy on Risk of Persistent Wheeze in the Offspring: A Randomized Clinical Trial. JAMA 26 January 2016 doi:10.1001/jama.2015.18318
Litonjua, A. A. et al. Effect of Prenatal Supplementation With Vitamin D on Asthma or Recurrent Wheezing in Offspring by Age 3 Years. JAMA 26 January 2016 doi:10.1001/jama.2015.18589
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