While there's evidence that the patch ups the chance most people will be able to kick the habit, researchers generally haven't found the same benefit in pregnant women.

"I don't think it's an issue so much with the way the nicotine patch works. The big issue is whether people are going to use it and adhere to it," said Dr. Gideon Koren, head of the Motherisk program at The Hospital for Sick Children in Toronto, who wasn't involved in the new report.

Without extra counseling encouraging women to stick to their quitting plan, he told Reuters Health, "the typical attempt is likely to fail."

Pregnant women may be extra likely to give up on the patch because as their metabolism increases, women's bodies process the nicotine in the patch much faster than they otherwise would -- making the therapy less effective at reducing cravings and withdrawal symptoms.

The good news, researchers said, is that nicotine-replacement therapy didn't seem to increase the risk of a miscarriage or stillbirth, or cause babies to be born any earlier or lighter.

That means that conducting an experiment with a higher-dose nicotine patch could be a next step, according to Dr. Tim Coleman from the University of Nottingham and his colleagues.

For their study, the researchers randomly assigned more than 1,000 pregnant British smokers, generally in their second trimester, to use a nicotine patch or an identical drug-free "placebo" patch for two months.

The women initially had an in-person counseling session, followed by phone check-ins about their cigarette use.

During the first month of treatment, 21 percent of women on the nicotine patch stopped smoking, compared to less than 12 percent with drug-free patches.

However, only nine percent of women in the nicotine patch group and eight percent in the placebo group were still smoke-free by the time they delivered -- a difference that could have been due to chance.

LOW ADHERENCE

Coleman's team found that only seven percent of women used their nicotine patches consistently for more than a month, and three percent kept using the drug-free patches after the one-month check in.

"It's really hard to help pregnant women quit smoking when they don't use the treatment," said Kathryn Pollak, who has studied smoking cessation at the Duke University Medical Center in Durham, North Carolina.

That's not for lack of drive, said Pollak, who wasn't involved in the new study. But the women who don't quit as soon as they find out they're pregnant are probably the ones who rely heavily on cigarettes and need lots of help with the process, she said.

Because nicotine is cleared from the body so much faster toward the end of pregnancy, Pollak said that this study may be an example of "under-dosing," and that the nicotine in standard patches might not work well enough to help women avoid cigarettes without suffering withdrawal.

But some researchers are wary of driving the dose up too high, because of possible effects on the fetus.

"We have to be really careful of how much nicotine we're giving," Pollak told Reuters Health. "We have to find that fine line of enough to help, but not too much."

In the UK study, there was no evidence of a higher risk of birth defects, premature birth or other pregnancy complications in women assigned to the nicotine patch, the researchers reported Wednesday in the New England Journal of Medicine.

Koren said that even at the dose used in the study --15 milligrams for 16 hours -- the patch may help women who also get regular, face-to-face counseling.

Psychotherapy is the typical treatment that doctors recommend for pregnant women trying to quit smoking, in part because it's drug-free.

"STICK IT OUT"

Nicotine patches typically run for about $2 per day, and can be bought without a prescription.

The study, which was funded by the National Institute for Health Research in the UK, doesn't suggest that it's time to give up on nicotine-replacement therapy completely, researchers said.

"Outside of pregnancy, (the patch) seems to work even at the dose we used very effectively, and even with very minimal behavioral support," Coleman told Reuters Health.

"If you're considering becoming pregnant, try your hardest to use any drugs that are available before you become pregnant," since afterward it may be that much harder to quit, he advised.

Pollak said that pregnant women can still benefit from nicotine replacement -- as long as they don't give up on it.

"Talk to your doctor about the costs and benefits and know that nicotine replacement only works when you do it for the length of time that's prescribed," she said.

"You just kind of have to stick it out."

SOURCE: bit.ly/cZYeY6 New England Journal of Medicine, online February 29, 2012.

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