The advice forms part of new guidance to help women and families give up smoking during and after pregnancy.

Smoking during pregnancy can increase the risk of miscarriage, premature birth, still-birth and sudden unexpected death in infancy.

Exposure to smoke in the womb is also associated with psychological problems in childhood such as attention and hyperactivity problems.

Professor Catherine Law, who chairs NICE’s Public Health Interventions Advisory Committee, said: ‘This guidance aims to protect the health of children by encouraging and supporting women and their families to give up smoking during or after pregnancy and for the long-term.

‘We know quitting can be difficult, which is why the guidance calls for a multi-disciplinary approach to provide a network of support to help expectant mums, or those who have a small child, quit for good. If they can do this, both they and their children can look forward to healthier futures,’ she said.

Professor Mike Kelly, director of the Centre for Public Health Excellence at NICE, said the plans were not designed to penalise pregnant women but to alert them to the high level of CO in their systems, which can harm the baby.

Other recommendations include formal training for healthcare and smoking cessation staff to ensure advice is offered in a non-judgmental way, and offering women personalised help, support and information on how to stop smoking.

Children of parents who smoke tend to suffer from more respiratory problems like asthma or bronchitis and have problems of the ear, nose and throat, compared to children in non-smoking households.

Nearly half of all children in the UK are exposed to tobacco smoke at home.

It costs the NHS up to £87.5m each year to treat mothers and infants with problems caused by smoking in pregnancy.