Quit-smoking aids don’t raise risk of major birth defects – study

Pregnant women who need help to stop smoking can be reassured quit aids such as nicotine patches and varenicline do not increase the risk of major birth defects in babies, thanks to an international study.

Led by the University of New South Wales National Drug and Alcohol Research Centre, and co-authored by the University of Otago, the study analysed 13,000 births from Australia, New Zealand, Norway, and Sweden.

The researchers compared the risk of birth defects in babies exposed to quit-smoking medicines nicotine replacement therapy, varenicline, and bupropion, to those born to women smoking in early pregnancy who did not use these quit-smoking tools.

The study, published in JAMA Internal Medicine, found no evidence that infants exposed to these medicines had higher rates of major congenital malformations.

Co-authors Dr Sarah Donald and Professor Lianne Parkin, of Otago’s Department of Preventive and Social Medicine, were delighted to be able to contribute their analysis of the New Zealand data to the study.

Dr Donald says it is an important research area for maternal and infant health.

“It was reassuring to find that the mothers’ use of quit-smoking medicines does not appear to increase birth defects in babies.

“The three quit-smoking therapies included in the study are available and fully funded in New Zealand, so these findings are very relevant for pregnant women here.

“Although smoking rates in New Zealand have declined over recent years, between 10-15% of pregnant women are smokers. Having more options to assist pregnant smokers to quit could lead to better outcomes for our mums and babies,” she says.

More information on the study

How did we conduct this research?

We analysed multiple sources of health data from women who gave birth between 2001 and 2020 in New South Wales Australia, New Zealand, Norway, and Sweden. We calculated the rates of major birth defects — both overall and in specific body systems — among babies of women who used a prescription NRT, varenicline, or bupropion in the first 13 weeks of pregnancy. These rates were compared to those among babies born to women who smoked during early pregnancy but did not use a prescribed quit-smoking medicine. We analysed the data for each country separately and combined the results.

What did we find?

The study included 9325, 3031 and 1042 babies of women who used NRT, varenicline and bupropion in in the first 13 weeks of pregnancy, respectively. Compared to babies of women who smoked during early pregnancy without using a quit-smoking medicine, we found no differences in the overall rates of major birth defects for NRT (3.76 per cent vs 3.44 per cent), varenicline (3.27 per cent vs 3.66 per cent), or bupropion (3.55 per cent vs 3.88 per cent).

When examining birth defects in specific body systems among babies of women using NRT, there were no significant differences in defects of the heart, limbs, genital organs, kidney and urinary tract, respiratory system, digestive organs or clefts. Similarly, the use of varenicline showed no differences for defects of the heart, limbs, genital organs, or kidney and urinary tract. For bupropion, the low number of women using the medicine made it impossible to draw conclusions about specific birth defects.

What do our findings mean?

Given the damaging effects of smoking during pregnancy, it is reassuring that we found no clear increase in the risk of birth defects following the use of NRT and varenicline in early pregnancy. This new evidence can help pregnant women who smoke, along with their healthcare providers, make informed decisions about using quit-smoking medicines during pregnancy.