Researchers have called for trials on giving supplements to pregnant women after a study at Southampton general hospital found evidence of bone weakness in children whose mothers had low vitamin D levels.

Pregnant women who had taken supplements or had been exposed to higher levels of sunlight were less likely to be short of vitamin D, researchers say in the Lancet.

However, Professor James Walker, of the Royal College of Obstetricians and Gynaecologists, warned that no woman should take extra vitamin D in pregnancy unless recommended by their doctor.