Seventy percent of moms-to-be who quit smoking during pregnancy pick it up again within the first year after childbirth, but breastfeeding could reduce that statistic, according to a new study.

"Breastfeeding seems to be a protective factor against increases in smoking after childbirth, so interventions should educate women about breastfeeding to maximize effectiveness," says Shannon Shisler of the State University of New York at Buffalo.

Of new moms who relapse, 67 percent revisit the habit just three months after their children are born and 90 percent resume by six months, according to the study, which was published in the journal Nicotine and Tobacco Research.

The study followed 168 women who smoked during their pregnancies from beginning to end.

"Although women decreased their tobacco consumption across their pregnancy, by nine months postpartum they had substantially increased their smoking," says Shisler, who adds that at this point they went back to smoking more than half of the cigarettes they smoke per day before conceiving.

Not sure how to predict changes in their smoking habits, the researchers took a variety of factors into account, including their use of other substances and whether or not their partners smoked.

Breastfeeding was the only factor that appeared to make a difference in smoking behavior, for those who did so for at least 90 days smoked less than those whose breastfeeding term was shorter or nonexistent.

"Increase in tobacco consumption after the birth of a child may have harmful effects on both the mother, and the infant who is at higher risk of exposure to environmental tobacco smoke," says Shisler.

Shisler says new moms who smoke should receive breastfeeding support during the first three months after giving birth and that promoting breastfeeding among pregnant smokers could be key in reducing postpartum relapses.

The study was published in the journal Nicotine & Tobacco Research.

Another study suggests new moms who quit during or just before pregnancy are more likely to stay smoke-free if support was made available during the first eight weeks postpartum.

"By decreasing secondhand smoking exposure and increasing breastfeeding duration, both of which have well documented short- and long-term benefits, this intervention can make a significant contribution to the health of infants and their mothers," said lead author Raylene Phillips, MD.

This study was presented October 4, 2010 at the American Academy of Pediatrics (AAP) National Conference and Exhibition in San Francisco.