Stopping smoking when already pregnant can boost baby's health

Babies born to mothers who stop smoking in early pregnancy are similar weight to those born to mothers who never smoked – study
Pregnant woman smoking
A study says quitting in the early stages of pregnancy can improve the resultant baby's birthweight. Photograph: Chad Ehlers/Getty Images

Women who stop smoking as late as when pregnancy is confirmed can dramatically boost the health of their baby, scientists said on Wednesday.

In the largest study of its kind, researchers led by Professor Nick Macklon, a consultant gynaecologist at the Princess Anne hospital in Southampton, 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 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 birthweight.

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

He said: "Not only was birthweight 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.

"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 birthweight, 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 socioeconomic data collected from pregnancies registered at Southampton University hospitals NHS trust between 2002 and 2010.

They also analysed seven groups of women, including non-smokers, those who quit 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.

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.

He said: "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 birthweight."

Macklon reported his findings at the annual conference of the European Society of Human Reproduction and Embryology in Stockholm.

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