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

The findings were part of the MAVIDOS study, which was launched in 2009 and involved more than 1,000 women from Southampton, Oxford, and Sheffield.

The study, led by the University of Southampton and University Hospital Southampton (UHS), revealed that children born to mothers who received vitamin D supplements during pregnancy showed greater bone mineral density in mid-childhood, as evidenced by bone density scans.

This meant their bones contained more calcium and other minerals, making them stronger and less likely to break.

Dr Rebecca Moon, NIHR clinical lecturer in child health at the University of Southampton led the analysis 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."

The research was published in The American Journal of Clinical Nutrition and underscores the importance of vitamin D supplementation during pregnancy as a public health strategy.

Vitamin D is crucial for regulating the body's calcium and phosphate levels, which are vital for the health of bones, teeth, and muscles.

The study involved pregnant women being randomly allocated to two groups: one receiving an extra 1,000 International Units of vitamin D per day, and the other a placebo.

Neither the pregnant women nor the doctors and midwives knew which group was which.

The research team followed up with 454 children aged between six and seven, all born to mothers who participated in the Southampton arm of the study.

The results confirmed that the beneficial effects on the children's bones were consistent at both four and six to seven years of age.

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

The Southampton research team are part of the MRC Lifecourse Epidemiology Centre (MRC LEC) and the NIHR Southampton Biomedical Research Centre (BRC).