Finally, a word to the wise: Don't rely on nicotine-replacement therapy or smoking-cessation drugs to control your weight when quitting.

They say that while nicotine-replacement therapies (NRTs) could be useful in the early stages of combatting withdrawal, public health bodies should reconsider their reliance on these techniques as a way to reduce the number of people who smoke.

Considered a first-line smoking cessation medication by the U.S. Public Health Service, it can be used instead of or in addition to nicotine-replacement therapies.

The study showed that women who used nicotine-replacement therapy in the first 12 weeks of pregnancy had a 60% greater risk of having babies with birth defects compared to women who were non-smokers.

If nicotine-replacement therapies haven't worked, consider the FDA-approved, non-nicotine options of bupropion (an antidepressant) and varenicline.

Because varenicline mimics the effect of nicotine, it is not recommended for use with other nicotine-replacement therapies.

The report, by Harvard School of Public Health showed that while nicotine-replacement therapies could be useful in the early stages of quitting, ex-smokers were twice as likely to relapse when they relied on them.

The study found that women who used nicotine-replacement therapy in the first 12 weeks of pregnancy had a greater risk of having babies with birth defects than women who did not.

That may be why analysts say that demand for nicotine-replacement therapies is unlikely to wither anytime soon.

Still, he said, the addition of bupropion to programs for ending the smoking habit represents the biggest development in the field since nicotine-replacement therapy was introduced in 1971.