Late Quitters Boost Unborn Babies' Health

Fertility and birth experts at Southampton’s university hospitals have found women who stop smoking as late as when pregnancy is confirmed can dramatically boost the health of their baby.

In the largest study of its kind, Professor Nick Macklon, a consultant gynaecologist and medical director of the Complete Fertility Centre at the Princess Anne Hospital, and his team studied the outcomes of 50,000 pregnancies.

They found that women who gave up smoking at the time of conception or when their pregnancy was confirmed – the periconceptional period – gave birth to babies with a similar weight to those born to mothers who had never smoked, cutting the risk of complications associated with low birth weight.

Healthy development during pregnancy without exposure to smoke also helps to limit the chances of premature birth, which can cause brain damage and congenital defects, such as cleft lip, and lead to other illness in later life.

Professor Nick Macklon said: "Not only was birth weight much better in this group than it was in the groups where the mothers had continued to smoke, but we also found that the babies reached the same gestational age and head circumference as those born to women who had never smoked,” said Prof Macklon, chair of the department of obstetrics and gynaecology at the University of Southampton.

“Mothers who smoke are encouraged to stop smoking when they become pregnant but, to date, there was little evidence that giving up at this late stage could have a positive effect on birth weight, so we can now give couples hard proof that making the effort to stop smoking once pregnancy is confirmed is beneficial for their baby.”

The team studied clinical, lifestyle, and socio-economic data collected from pregnancies registered at Southampton University Hospitals NHS Trust between 2002 and 2010 and analysed seven groups of women, including non-smokers, those who stopped more than a year prior to conceiving, those who stopped less than a year prior to conceiving, smokers who stopped once the pregnancy was confirmed and those who continued to smoke.

Prof Macklon also warned of the worrying trend of women who continue to smoke because they want to give birth to a smaller baby – despite overwhelming evidence of the consequences:

“It is important that people who believe that a smaller baby means an easier birth take into account the increased risks of complicated deliveries in smokers as well as the risk of disease later in life which goes with low birth weight.”

Prof Macklon, who launched Complete Fertility Centre in Southampton in May, reported the findings on Wednesday, 6th July, at the annual conference of the European Society of Human Reproduction and Embryology in Stockholm.