Pregnant teenagers are deliberately smoking in the hope of having smaller babies so giving birth is easier, a minister has claimed.
Public health minister Caroline Flint spoke at a Labour Party conference fringe meeting about teenagers' attempts to reduce their labour pains, the Nursing Standard magazine reported.
Smoking can lead to low birthweight babies, meaning some teenagers smoke throughout pregnancy, the magazine said.
The Department of Health said Ms Flint had heard about the issue anecdotally from health professionals and young women she has met.
Ms Flint 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.
Smoking can also cause other problems, such as respiratory illness.
Women who smoke are less likely to carry their babies to full term and there is a 26 per cent increased risk that they will miscarry or have stillbirth. Babies of smoking mothers are also an average of 200g (7oz) lighter at birth.
Royal College of Midwives (RCM) midwife Gail Johnson said there was no evidence that having a smaller baby reduced pain in labour.
She said: "Midwives are a vital key to advise women about smoking, diet and lifestyle - issues which are important for the health of the woman and her baby but also impact on the wider public health of families.
"Many midwives offer classes designed specifically to meet the needs of teenagers and challenge their peer group chats about keeping down their weight by smoking rather than healthy eating and exercise.
"Midwives know how important it is to support pregnant women and they can link with other agencies to provide advice on smoking cessation. It is vital that the risks associated with smoking are highlighted and women are then supported to make changes to their lifestyle."