All pregnant women should have breath tests to see whether they are smokers or not, the UK's health watchdog said.
The National Institute for Health and Clinical Excellence (Nice) said that every expectant mother should be encouraged to have a carbon monoxide test to see whether they smoke so they can get the appropriate advice for quitting.
However, the recommendation was criticised by midwives who said that medical practitioners should encourage women to quit smoking instead of making them feel guilty.
The watchdog said the new guidelines are not aimed at penalising smokers but hope to help women and their families give up smoking during and after pregnancy.
Nice director of the centre of public health excellence Professor Mike Kelly said: "During pregnancy, smoking puts the health of the women and her unborn baby at great risk both in the short and long-term, and small children who are exposed to second-hand smoke are more likely to suffer from respiratory problems.
"One of our recommendations is for midwives to encourage all pregnant women to have their carbon monoxide levels tested and discuss the results with them.
"This isn't to penalise them if they have been smoking, but instead will be a useful way to show women that both smoking and passive smoking can lead to having high levels of carbon monoxide in their systems."
However, Royal College of Midwives (RCM) education and research manager Sue Macdonald said the use of the breath test may make women feel "guilty".
Ms Macdonald said: "Strategies for smoking cessation should apply to all women regardless of being pregnant. There is no doubt that most women are aware of the effects of smoking. The challenge is to reduce the numbers doing it.
"There appears to an emphasis on pregnant women, which is appropriate given the evidence. However, the key issue here for Nice is their emphasis on the CO2 monitor.
"It is crucial that health practitioners, including midwives, focus on being supportive rather than making women feeling guilty, or as though they may not be truthful.
"Use of the CO2 monitor has the potential to make women feel guilty and not engaged. We need to look at a range of individualised interventions for women that meet their needs and aspirations.
The RCM welcome the guidelines because reducing smoking helps the health of women and their babies but are also sceptical about the use of the breath test monitors because of cost.
Ms Macdonald added: "There is also the cost implication of all midwives carrying monitors, and issues such as safety and infection control, and whether this is the best use of funds to address smoking cessation."
Jane Brewin, chief executive of baby charity Tommy's, said: "Every baby deserves the best start in life and those born to smokers tend be smaller and weaker than other infants.
"However, it's important pregnant women feel supported if they make the decision to quit, and are aware of the stop smoking services available to them."
If the recommendations come into practice every mum-to-be will have the breath test at their first antenatal appointment.Reuse content