Pregnant Women
Pregnant or breastfeeding women have been urged to boost their vitamin D.
Rickets is a bone disease mainly caused by a lack of the vitamins. It can lead to deformities, stunted growth and general ill-health.
Some minority ethnic groups in the UK, including Asians, are particularly at risk, says the Department of Health.
Doctors want pregnant women to take more vitamin D during winter months.
It is made by the skin in response to sunlight, but can also be found in certain foods.
Officials are urging women to check if they are eligible for free supplements from their GP or health visitor under the government's Healthy Start scheme.
It provides vitamin D-rich milk and fresh fruit and vegetables as well as supplements for those on benefits or women who are under the age of 18 years old and pregnant.
Common at the start of the last century, rickets was thought to be eradicated in the 1950s because of better nutrition.
But research suggests the incidence of rickets could be as high as one in 100 children among Asian, Afro-Caribbean and Middle Eastern ethnic minority groups.
Dark-skinned people do not absorb as much sunlight through the skin and may also wear clothing that limits exposure to the sun for cultural reasons.
Mothers and babies are simply not getting enough of this important vitamin
Most people in the UK should get enough vitamin D from sunlight - it only takes 15 minutes of sun exposure to the arms, head and shoulders each day during the summer months to make enough vitamin D for good health.
But in winter months at latitudes of 52 degrees north (above Birmingham), there is no ultraviolet light of the appropriate wavelength for the body to make vitamin D in the skin, research shows.