The Government has said that pregnant women should increase their intake of vitamin D in the winter months to prevent their child from suffering from rickets.
And the Department of Health (DH) urged women to consider taking supplements if they are expecting or breastfeeding.
Although no exact data is currently available, the Department said health workers are seeing more children than ever with a vitamin D deficiency.
A lack of the vitamin can cause seizures and rickets, which leads to bones not developing properly.
In the summer months, just 15 minutes exposure to sunlight per day is enough for the body to make enough vitamin D for good health, while in the winter months, foods like oily fish, and eggs can provide enough of the vitamin alongside the body's own stores.
But pregnant and breastfeeding women and children under four may also benefit from a supplement containing 10 micrograms of vitamin D, the Department said.
It urged women to contact their GP for a blood test if they think they may be lacking the vitamin.
Dr Colin Michie, a paediatrician at Ealing Hospital in west London, said: "If a pregnant or breastfeeding woman is lacking in vitamin D, the baby will also have low vitamin D and calcium levels which can lead them to develop seizures in the first months of life."