43% 'resume smoking after giving birth'
Nearly half of women who quit smoking during pregnancy take it up again soon after they give birth, according to research in the journal Addiction.
The analysis of several studies suggests 13% of women who enrol on smoking cessation programmes quit during pregnancy.
But 43% of these restart within six months of giving birth.
Public Health England says more action is needed to help mothers-to-be quit for good.
Smoking during pregnancy has been linked to many health problems including premature births, miscarriages, stillbirths and sudden infant deaths.
The scientists from the universities of Nottingham and York looked specifically at the success of women who used smoking cessation services to help them quit.
They pulled together several international trials, including some from the UK, involving almost 1,000 women who took part in stop smoking programmes between 1989 and 2014.
And they found only a minority of women who tried to quit smoking succeeded.
Official figures for England published by the Health and Social Care Information Centre show 11% of pregnant women were recorded as smokers at the time of giving birth in 2014-15, a steady decline from 15 percent in 2007.
But regional data shows wide differences across the country - with more smokers in poorer areas.
Prof Jonathan Grigg of the Royal College of Paediatrics and Child Health said the findings of this study were a worrying sign for the state of child health.
He added: "We need to fully support parents in the first few months with their baby to highlight to them the importance of keeping their home smoke-free.
"Health visitor and smoking-cessation services are vital to this process, but with the £200m reduction in funding for public health, these services are at risk."
Rosanna O'Connor, at Public Health England, said: "While the rate of women smoking during pregnancy continues to fall, further action is needed to support those who find it more difficult to stop and to help those who do stop, to stop smoking forever.
"It is vital to protect babies from smoke during pregnancy and in the early months of life. The best protection for mothers, their babies and partners is to quit smoking for good."