A review of programs that tried to help pregnant women quit smoking has found nearly half of them who succeeded became smokers again within six months of their baby being born.

The review, published Tuesday by the scientific journal Addiction, looked at stop-smoking support programs run by the U.K.'s National Health Service for 18,887 pregnant smokers.

Researchers found that among the women who were offered the help, only 13 per cent were able to quit sometime during the pregnancy and remain off the cigarettes until giving birth.

The remaining 87 per cent of women either tried to kick the habit and failed, or they did not attempt to quit.

Of those who did manage to quit, the review found 43 per cent started smoking again within six months of childbirth.

"Most pregnant smokers do not achieve abstinence from smoking while they are pregnant, and among those that do, most will restart smoking within six months of childbirth," the study's authors said.

"Our report reveals a wide gulf between what pregnant women need to quit smoking and what our healthcare services currently provide," they wrote.

Researchers from the University of Nottingham and the University of York conducted the study, commissioned by the National Institute for Health Research (NIHR), which is funded by the U.K. department of health.

Despite public health messages that warn of harm such as miscarriage and premature birth, an estimated 10 per cent of women in the U.S. and Canada, and 17 per cent of women in the U.K., still smoke during pregnancy.‚Äč