WOMEN who smoke have been warned their habit is most likely to cause harm to their babies during the first three months of their pregnancy.
It has long been known that cigarette smoke harms an unborn baby, and now experts have found babies are most at risk if their mothers smoke in early pregnancy.
A study of almost 22,000 children in eight European countries found these babies are at a high risk of developing asthma by the time they reach school age.
Experts say the first weeks of pregnancy are the most damaging, a time when some women do not realise they are expecting.
One in 40 of the mothers studied smoked while she was pregnant, and after studying this and other factors – age, education and diet – researchers found this led to an increased risk of asthma and wheezing in her children.
Lead author Dr Asa Neuman, of the Institute of Environmental Medicine in Stockholm, said: “These results indicate the harmful effects of maternal smoking on the foetal respiratory system begin early in pregnancy, perhaps before the women is even aware that she is pregnant.”
“Teenagers and young women should be encouraged to quit before getting pregnant.”
The findings are published in the American Journal of Respiratory and Critical Care Medicine.