Women who quit smoking during pregnancy frequently take up the habit again after delivery. Now new research suggests that fears about weight gain may be a motivating factor for many.

Researchers interviewed women who stopped smoking soon after learning they were pregnant. Those who said they were highly motivated to stay off cigarettes following delivery were also the least likely to consider smoking a weight-control tool.

Those who expressed fears they would not be able to control their weight if they didn’t smoke were, not surprisingly, less motivated to remain nonsmokers after pregnancy.

“Two-thirds of women who quite smoking when pregnant will resume smoking after giving birth,” said Michele Levine, PhD, assistant professor of psychiatry at the University of Pittsburgh School of Medicine.

“We wanted to understand how factors such as depression or the baby blues, and weight concerns, might affect women’s motivations to smoke after delivery.”

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Smoking and Pregnancy

The risks of smoking during pregnancy are well known.

Twenty percent to 30 percent of low-weight births, as many as 14 percent of preterm deliveries, and about 10 percent of infant deaths are caused by exposure to cigarette smoke in the womb, according to the American Lung Association.

But the dangers for babies don’t end at delivery.

Mothers who smoke can pass nicotine to their babies through breast milk. And infants exposed to secondhand smoke are more likely to develop colds, bronchitis, and other respiratory diseases, including asthma.

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Study Results vs. Conventional Wisdom

Nicotine addiction cannot explain why so many women who stop smoking during pregnancy resume the habit after they give birth.

“Conventional wisdom tells us that it should be easy to abstain if you have gone without cigarettes for six months or so,” Levine tells WebMD. “But it is clear that many women who say they don’t want to start smoking again end up doing just that.”

The 119 women included in the study by Levine and colleagues had smoked at least eight cigarettes a day for an average of nine years, and all quit when they learned they were pregnant. About half were white and half were black.

The women were interviewed in their third trimester of pregnancy. The results are reported online in the October edition of the journal Annals of Behavioral Medicine.

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Weight Concerns Common

Nine out of 10 women reported that they quit smoking on their own without help from formal programs.

Based on their responses to a written questionnaire, 65 percent were judged to be highly motivated to stay smoke-free after delivery, and 74 percent of these women felt confidant they would be able to do so.

Women who reported less confidence about weight issues also tended to be less motivated to remain nonsmokers after delivery.

The researchers have continued to follow the women since delivery in an effort to determine if concerns about weight affect actual behavior. Those findings have not been published.

“If it turns out that concerns about weight are a big reason why women start smoking again after pregnancy, then we need to address that,” Levine says. “We know that there are ways to help women better understand the issue and feel less worried about it.”

Programs designed to help new moms stay smoke-free should confront issues on weight and body image, the researchers suggest.

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By Salynn Boyles, reviewed by Louise Chang, MD

SOURCES: Levine, M. Annals of Behavioral Medicine, October 2006; online edition. Michele D. Levine, PhD, assistant professor of psychiatry and psychology, Western Psychiatric Institute and Clinic, University of Pittsburgh Medical Center. American Lung Association: “Women and Smoking Fact Sheet,” March 20, 2006.