Children whose mothers took extra vitamin D during pregnancy continue to have stronger bones at the age of seven, according to new research.

Bone density scans taken for the study led by the University of Southampton and University Hospital Southampton (UHS) showed they contained more calcium and more minerals, making them stronger and less likely to break.

The researchers say the findings, published in The American Journal of Clinical Nutrition, reinforce the importance of the use of vitamin D supplements in pregnancy as a public health strategy.

Our findings show that the benefits of vitamin D supplementation during pregnancy persist into mid-childhood

Dr Rebecca Moon, NIHR (National Institute for Health and Care Research) clinical lecturer in child health at the University of Southampton, said: “Our findings show that the benefits of vitamin D supplementation during pregnancy persist into mid-childhood.

“This early intervention represents an important public health strategy. It strengthens children’s bones and reduces the risk of conditions like osteoporosis and fractures in later life.”

Vitamin D regulates the amount of calcium and phosphate in the body – minerals essential for bones, teeth and muscle health.

In 2009, researchers launched the Mavidos (Maternal vitamin D osteoporosis) study, which recruited more than 1,000 women from Southampton, Oxford and Sheffield.

During their pregnancy, the women were randomly divided into two groups, with one group taking an extra 1,000 International Units of vitamin D per day and the other taking a placebo tablet.

The pregnant women, and the doctors and midwives looking after them, did not know which group they were in.

Previous research assessed the children’s bone health at the age of four and the results showed that bone mass was greater in children born to mothers who had had vitamin D supplementation during pregnancy compared with those who had not.

Pregnant women in the UK are now routinely advised to take vitamin D supplements

For the latest study, the researchers investigated whether the effects on bone health continued into mid-childhood and followed up with 454 children aged six and seven, all of whom were from the Southampton area.

A University of Southampton spokesman said: “The results confirmed that the beneficial effect on children’s bones was similar at ages four and six to seven.

“Pregnant women in the UK are now routinely advised to take vitamin D supplements.”

– The research was funded by Versus Arthritis, the Medical Research Council, the National Institute for Health and Care Research, and the Bupa Foundation.