2. March 2020
Vitamin D in pregnancy does not affect childhood asthma risk

In 2016, an American study inspired hope that children would be protected against asthma if their mothers took vitamin D while pregnant. The recently published long-term results do not support this theory.

What did the researchers want to find out?

Augosto Litonjua, a pulmonary specialist at Golisano Children’s Hospital at the University of Rochester in the US, and his team wanted his verify his own data on the prevalence of asthma in children.


In 2016, the team discovered that children whose mothers had taken vitamin D during pregnancy suffered less frequently from asthma in the first year of life than children of mothers who had only received a placebo. However, the effect had nearly disappeared three years later (Litonjua, 2016).


This warranted further observation of the children in order to determine the actual effect of vitamin D intake during pregnancy on the risk of asthma (Litonjua, 2020).


How did they proceed?

The research team examined the children again at six years of age to determine


  • whether they had difficulty breathing, indicating an asthma disease or
  • whether they had already been diagnosed with asthma.


The study included 405 children whose mothers had taken 4,400 IU of vitamin D daily during pregnancy. The result was compared with findings from 401 children whose mothers had received a placebo during pregnancy.


In addition, all pregnant women took a multivitamin, which contained a small amount of vitamin D (400 IU).


Litonjua and his team also investigated the prevalence of inflammatory skin diseases (eczema), hay fever (allergic rhinitis) and respiratory infections.


What was the result?

At six years of age, 360 of the children had developed asthma or recurrent wheezing. It made no difference whether the mother had taken a high dose of vitamin D or not during pregnancy.

Eczema, allergic rhinitis and respiratory infections were equally prevalent in both groups.


Why is this study important?

Children whose mother or father already has an allergic disease have an increased risk of asthma. This risk clearly cannot be reduced by taking vitamin D during pregnancy.


But it may be important to take vitamin D for other reasons. Long-term vitamin D deficiencies inhibit normal bone growth in children. In adults, insufficient vitamin D levels can cause bones to become brittle, leading to osteoporosis.


Exposure to fresh air and sunshine is an effective way to replenish vitamin D stores. UVB rays from the sun help the skin convert existing precursors into active vitamins in the body. In this way, 80 to 90 per cent of the body’s vitamin D needs can be covered (RKI 2019).


Original studies

Litonjua AA et al. Effect of Prenatal Supplementation With Vitamin D on Asthma or Recurrent Wheezing in Offspring by Age 3 Years. JAMA. 2016;315(4):362-70.


Litonjua AA et al. Six-Year Follow-up of a Trial of Antenatal Vitamin D for Asthma Reduction. N Engl J Med. 2020;382(6):525-33.


Wuertz C et al. Cross-sectional study of factors that influence the 25-hydroxyvitamin D status in pregnant women and in cord blood in Germany. Br J Nutr. 2013;110(10):1895-902.


Robert Koch Institut. The Robert Koch Institute: Answers to frequently asked questions about vitamin D, 25 January 2019 (retrieved on 19 February 2020) (in German)