Pregnant teenagers smoke to try to reduce the size of their babies, and make delivery less painful, a government minister has claimed.
Smoking rates are stubbornly high among teenagers
Nursing Standard magazine reports that Public health minister Caroline Flint made the claim at a fringe meeting at last week's Labour Party conference.
There is evidence that smoking in pregnancy can stunt a baby's growth.
However, low birth weight is strongly linked to an increased risk of many health complications and miscarriage.
Ms Flint told the meeting she had heard about the issue anecdotally from health professionals, and from young women she had met.
She said: "It is important that we understand what stops young women making healthy choices so we can provide the right answers to their concerns.
"In this case, childbirth is no less painful if your baby is low weight. So smoking is not the answer, pain relief is."
Studies have shown that women who smoke during pregnancy are three times more likely to have a low birthweight baby.
They also face a 26% increased risk of miscarriage, or stillbirth, and a raised risk of giving birth prematurely.
Gail Johnson, of the Royal College of Midwives, said there was no evidence that having a smaller baby reduced pain in labour.
Charlotte Davies, of Tommy's, the baby charity, said their work suggested that one in 10 women smokes throughout pregnancy.
Lack of education
Belinda Phipps, chief executive of the National Childbirth Trust, said it showed a worrying lack of education among young women.
She said: "Although smoking does reduce the baby's size, it does have a devastating effect on the baby in lots of other ways.
"We are bringing up our young women very fearful of labour.
"Labour is a normal process which is hard work, and for many people painful, but, with the right sort of support and the right sort of care, is perfectly doable.
"It is a real indictment of our education that teenagers are so fearful that they are prepared to do something that is enormously damaging to themselves and and their babies because they think there might be an outside chance it might make their labour easier. Which is largely a myth."