Pregnancy can be a big motivator for women to stop smoking. Now a new study suggests that at least some pregnant smokers start cutting back even before they know they've conceived.
The findings, researchers say, suggest there may be biological mechanisms during pregnancy that can blunt the desire for nicotine.
If true, understanding those processes could potentially lead to new ways to aid smoking cessation, according to the investigators.
However, the findings do not imply that pregnancy makes quitting easy, said lead researcher Dr. Suena Huang Massey, a psychiatrist and associate professor at Northwestern University Feinberg School of Medicine, in Chicago.
Instead, she said, the findings show that, on average, smokers cut down a bit during the time between conception and when they learn they are pregnant. The reasons for that remain an open question.
It's possible that during early pregnancy, some smokers feel nauseated by the smell or taste of cigarettes, according to Massey.
In addition, levels of a hormone called human chorionic gonadotropin (hCG), which is related to morning sickness symptoms, peak between the fifth and 10th weeks of pregnancy. That, Massey noted, coincides with the period where women in this study began to curb their smoking, before knowing they were pregnant.
"That may be a coincidence," she said. "But it's an interesting finding."
The study — published Oct. 17 in the journal Addiction Biology — involved 416 U.S. women who were pregnant and were smokers when they conceived. They were interviewed about their daily smoking habits, going back to the months before their estimated date of conception.
On average, Massey's team found, the study participants cut back by one cigarette per day during the weeks between conception and learning they were pregnant.
"They cynic might say, that's probably because they were planning on becoming pregnant and were trying to quit smoking," Massey said.
So her team did another analysis focused only on women with an unplanned pregnancy. And the results were the same.
If there is a biological driver behind the findings, that does not mean Mother Nature is making things easy for pregnant women, Massey said. In fact, despite wanting to quit, many pregnant women do not.
In this study group, women typically cut down on cigarettes after learning they were pregnant — but only a minority had completely quit by the end of the first trimester.
In fact, some women end up smoking more, because pregnancy speeds up their metabolism of nicotine, said Dr. Panagis Galiatsatos, a pulmonary specialist at Johns Hopkins Medicine in Baltimore.
Ideally, women should receive help with smoking cessation before pregnancy, said Galiatsatos, who is also a spokesman for the American Lung Association and was not involved with the study.
"That's the opportune time," he said.
That's not only important for the health of the pregnancy, Galiatsatos pointed out, but for the young adult smoker.
But the reality is, about half of pregnancies in the United States are unplanned, Massey said. So many young women who smoke may find themselves trying to quit only after conceiving.
Counseling is a key part of helping them quit, Galiatsatos said. People smoke in response to "triggers," he noted, and learning to recognize those triggers and deal with stress in healthier ways are vital to kicking the habit for good.
"People need to learn how to be non-smokers during good times and bad times," Galiatsatos said.
If counseling is not enough, pregnant women may be able to use nicotine replacement therapies or medications approved by the U.S. Food and Drug Administration for smoking cessation. Any concerns about medication, Galiatsatos noted, would have to be balanced against the risks of continued smoking.
"You really need to consult your own doctor about the risks and benefits," he said.
As for the current findings, Massey said more research is needed to understand how pregnancy, itself, might influence smoking habits.
Very little is actually known, she noted, since studies generally focus on how smoking affects pregnancy and the baby.
Smokefree.gov has smoking cessation help for pregnant women.
SOURCES: Suena Huang Massey, MD, associate professor, psychiatry and behavioral sciences, and medical social sciences, Northwestern University Feinberg School of Medicine, Chicago; Panagis Galiatsatos, MD, MHS, assistant professor, division of pulmonary and critical care medicine, Johns Hopkins University School of Medicine, Baltimore, and national spokesman, American Lung Association, Chicago; Addiction Biology, Oct. 13, 2022, online