Family Matters

A New Study Details the Effects of Smoking in Pregnancy

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Pretty much everyone knows that smoking is bad for you. It’s particularly ill-advised for pregnant women, although data show one in five U.S. moms-to-be still cop to the habit. Lest smokers need another nudge to quit, the first systematic review of the research now details exactly how cigarette smoking puts baby at risk.

The new paper, assembled by researchers at University College London, includes studies from the past 50 years that looked at the effect of smoking on pregnancy outcomes. “It doesn’t change the basic tenet that smoking is bad, but it fleshes out the details and provides you with a lot of information that can be defended,” says Michael Katz, senior vice president for research and global programs of the March of Dimes. “If someone came to you and said, ‘There’s no evidence,’ you can say, ‘Well, there is evidence.’”

Evidence of what? Of oral clefts — cleft lip and cleft palate — for one thing. The review, published Monday in the journal Human Reproduction Update from the European Society of Human Reproduction and Embryology, revealed a strong link between smoking and oral facial abnormalities that can arise when a flat embryo becomes a tube in the third week of pregnancy. It’s a precarious time for an embryo, and smoking can disturb the process.

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Congenital heart disease is also distinctly associated with moms who smoke. Researchers had long suspected that was the case, but the extensive review process revealed papers that corroborate the connection. Both oral clefts and congenital heart disease are treatable, but heart disease is far trickier to address. Children who need complicated, costly surgery must spend considerable time in the hospital, and not all cases can be fully corrected.

The London study looked at nearly 174,000 cases of malformations, compared with close to 12 million control cases, to conclude that cigarette chemicals including nicotine, carbon monoxide and tar can lead to limb deformities, clubfoot and gastrointestinal and optical disorders, not to mention stillbirth — when a baby dies in utero more than halfway through the pregnancy — and premature birth.

Even secondhand smoke is hazardous: earlier this year, a study by University of Nottingham researchers found that the risk of stillbirth jumped 23% when pregnant non-smokers breathed in sidestream smoke at home or at the office.

Women who smoke can also have a more difficult time getting pregnant in the first place and may also be more likely to have ectopic pregnancies, vaginal bleeding or problems with the placenta. And they’re at risk of other nasty side effects, like raising uncoordinated kids who may go on to become criminals. Healthland’s Meredith Melnick reported last year that women who smoked more than 20 cigarettes a day while pregnant were more likely than women who smoked less to have adult children who’d seen the inside of a jail cell.

In fact, adults whose mothers were heavy smokers during pregnancy were 30% more likely to have been arrested than those whose mothers were light or nonsmokers. Further, they were more likely to be repeat offenders.

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Worldwide, 250 million women use tobacco daily, according to statistics from the 14th World Conference on Tobacco or Health held in 2009 in Mumbai. Katz is hopeful that the vast body of research compiled on the pitfalls of puffing while pregnant will result in at least some of them quitting. “Will this persuade pregnant women more than a simple statement? I don’t know,” he says. “Some women are so addicted that it overcomes their good judgment. Addiction is a very strong negative force.”

Bonnie Rochman is a reporter at TIME. Find her on Twitter at@brochman. You can also continue the discussion on TIME‘s Facebook page and on Twitter at @TIME.