Pregnant smokers can reverse risks if they quit by 15 weeks

WOMEN who kick the smoking habit within 15 weeks of becoming pregnant can reverse the increased risk to smokers of giving birth to an underweight or premature baby.

In addition, contrary to common belief, those who quit smoking within this time frame can do so without suffering increased stress.

The findings have emerged as part of a major international study geared towards developing screening tests to predict small-for-gestational-age infants, spontaneous pre-term birth and pre-eclampsia (hypertension during pregnancy).

According to the research, women who do not quit smoking by 15 weeks of pregnancy are three times more likely than non-smokers to give birth prematurely and twice as likely to have low birth-weight babies. In contrast, women who quit smoking during this time frame bring their risk of these complications back down to the same level as non-smokers.

The study, which involves six universities worldwide, and includes researchers from University College Cork (UCC), has also identified a set of proteins in the blood of pregnant women that may predict the development of pre-eclampsia.

Pre-eclampsia, sometimes called toxemia, is a potentially life-threatening condition that only occurs during pregnancy and which, in severe cases, can cause swelling of the liver, or in rare cases, rupture of the liver, seizures and kidney failure.

Professor Louise Kenny of the obstetrics and gynaecology department at UCC said the findings show maternity care providers should see women early in pregnancy and also emphasise the importance of giving up smoking within 15 weeks.

“For the first time it has been shown that pregnant women who stop smoking during this window of opportunity can prevent serious late pregnancy complications,” said Prof Kenny.

Up to now, most studies have focused on the harmful effects of smoking during pregnancy, including increased risk of miscarriage, ectopic pregnancy, stillbirth and neo-natal death. This study shows that quitting within a critical time period can prevent complications.

Prof Kennedy said the additional finding that women who stop smoking by 15 weeks of pregnancy are not more stressed than those who continue to smoke was “an important message”, challenging the widely held assumption that quitting smoking increases stress.

In relation to the study’s progress in identifying a set of proteins in the blood that may predict pre-eclampsia, Prof Kenny said the study opened the way for the development of a potential screening test for pre-eclampsia.

“At present, there is no method to identify first-time mothers who will develop this serious condition. If women at high risk of pre-eclampsia could be identified early in pregnancy, they could be offered intervention to prevent it and more intensive monitoring to enable earlier detection of the condition,” said Prof Kenny.

Pre-eclampsia occurs in between 4% and 7% of first-time pregnancies.

The international study, SCOPE, will monitor 10,000 women worldwide, 3,000 of whom will be recruited in Cork. The current results come from more than 2,500 women in New Zealand and Australia who were surveyed at 15 weeks’ gestation. Results for 500 women, already recruited from Cork, will be added to the study to examine this effect in Irish women.