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Smoking and Pregnancy

  • Bruce Mirken
  • Posted March 11, 2013

You probably know that drinking during pregnancy can cause birth defects in your unborn child. But do you know what smoking during pregnancy can do? To test yourself, choose which of the following are true if you smoke while you're pregnant:

1) You're more likely to give birth to a "preemie," a premature baby, who runs a greater risk of birth complications and serious illness.

2) You're more likely to have a miscarriage or to deliver a stillborn baby.

3) Your baby runs a greater risk of developing Sudden Infant Death Syndrome, or SIDS.

4) You're more likely to develop preeclampsia, a potentially life-threatening condition related to high blood pressure.

5) All of the above.

If you guessed "all of the above," you're correct. Just as drinking during pregnancy can cause permanent brain damage and retardation in your developing baby, smoking can damage the fetus as well as the mother. In doctor-speak, smoking during pregnancy is considered "the single largest modifiable risk factor for pregnancy-related illness and death in the United States," according to a study published in the journal Drug Safety. In plain English, that means it's the largest risk facing you and your baby that you have the power to change.

Even if you are pregnant now and still smoking, don't assume the damage is already done. Quitting, even while you are pregnant, can improve your chances of delivering a healthy baby.

"You shouldn't smoke while you're pregnant, that's really clear," says Serena Chen, a spokeswoman for the American Lung Association. "But the nature of nicotine addiction is such that only about one third of pregnant women who smoke will quit. We need to give pregnant women all the help we can."

Of course, that wasn't always the prevailing attitude. In the 1940s, the mother of one of Chen's coworkers was advised by her doctor to smoke during her pregnancy. Smoking, the doctor said, would relax her. (Similarly, many women were once told that it was fine to have beer daily while pregnant or nursing; today, the federal government urges women to avoid alcohol completely while they're pregnant or nursing.)

But today we know that cigarette smoke contains some 4,000 chemicals, 40 of which can cause cancer and a wide variety of which are known to be reproductive toxins. The latter include carbon monoxide, ammonia, lead, hydrogen cyanide and, of course, nicotine. Unfortunately, according to the American Lung Association and others, the mother's bloodstream delivers these toxic chemicals to the developing fetus quite efficiently.

Miscarriages and premature births

Women who smoke during pregnancy are at higher risk than nonsmokers for a variety of problems, including miscarriage, stillbirth, premature rupture of membranes, premature labor and delivery and preeclampsia, a serious condition related to high blood pressure that is a leading cause of fetal complications in the United States, according to the Drug Safety study. The Campaign for Tobacco-Free Kids and others estimate that tobacco is responsible for a minimum of 19,000 miscarriages each year.

Babies born to smoking mothers are at increased risk for premature birth, sudden infant death syndrome and a variety of other health problems. The main danger, says Chen, is low birth weight. According to the Centers for Disease Control and Prevention, 12 percent of babies born to smokers weigh less than five pounds, eight ounces -- the cut-off point for low birth weight -- compared to 7.2 percent for nonsmokers. That, Chen adds, means "more vulnerability to all kinds of illnesses, a whole host of problems."

Not only are the babies of smokers more likely to be born prematurely, a study published by the American Lung Association indicated that the lungs of premature babies born to smokers don't function as well as those of "preemies" born to nonsmokers. Women with preeclampsia who smoke have a higher risk of problems during their pregnancy than those who don't.

In later childhood, the children of mothers who smoke during pregnancy are also more likely to be plagued by a variety of neurological and behavioral problems. Some research has shown learning and memory impairment and delays in language development, among other difficulties, although results have been somewhat inconsistent from one study to another. One particularly exhaustive study, published in the August 2001 issue of Developmental and Behavioral Pediatrics, followed a group of children up to age 10. That study found that "maternal smoking during pregnancy has a small, statistically significant, adverse effect on learning, memory, problem solving, and eye-hand coordination," which researchers termed "an important burden on this group of children." According to Chen, the abundant evidence that tobacco contributes to "defects in neurological development" is a real cause for concern.

It's never too late

The good news is that quitting smoking, even mid-pregnancy, reduces some of the harm, including the risk of preterm delivery. In a large Swedish study published in the American Journal of Epidemiology that examined over 15,000 births, babies born to smokers were -- as expected -- shorter, weighed less, and had smaller heads on average than the children of nonsmokers. But those born to women who stopped smoking by the 32nd week of pregnancy, though still shorter, had normal weight and head size.

So quitting can be crucial to your baby's health and development, but as any smoker who has tried to quit knows, it's easier said than done. Are stop-smoking aids such as nicotine gum or patches safe to use during pregnancy? The answer, unfortunately, is not so clear.

Nicotine is classified by the Food and Drug Administration as a "Category D" drug, meaning it carries some risks during pregnancy. For this reason, Public Health Service guidelines urge doctors to use caution in prescribing the drug to pregnant patients and to encourage pregnant smokers to quit without nicotine replacement therapy (NRT).

But some experts believe NRT can be used with reasonable safety during pregnancy. A detailed review of the evidence published in the journal Drug Safety notes that much of the reproductive harm from smoking appears to be caused by chemicals in smoke other than nicotine. The authors urge more research, but conclude that use of NRT during pregnancy is "reasonable."

The authors also offer some reassurance to breast-feeding mothers, noting that breast milk exposes infants to only small amounts of nicotine. They conclude that any risk from NRT to breast-feeding infants is far less than that of secondhand smoke. So if you're trying to quit, ask your doctor about all the options. The authors of the Drug Safety review put it simply: "Nicotine replacement products are not completely without risk, but their risk is much less than that of cigarette smoke."

References

Interview with Serena Chen, spokeswoman for the American Lung Association

Miller, EC et al. The risk of adverse pregnancy outcomes is increased in preeclamptic women who smoke compared with nonpreeclamptic women who do not smoke American Journal of Obstetrics and Gynecology. Vol. 203, Issue 4. October 2010

Lindley, A., et al, Effect of continuing or stopping smoking during pregnancy on infant birth-weight, crown-heel length, head circumference, ponderal index and brain: body weight ratio, American Journal of Epidemiology, 2000, 152(3):219-225

American Lung Association, Smoking and Pregnancy, www.lungusa.org/tobacco/smosmpreg.html.

Dempsey and Benowitz, Nicotine and smoking cessation in pregnancy, Drug Safety, 2001, 24(4):279-321.

American Lung Association, Tobacco smoke exposure can harm babies? lungs two months before birth, 9/14/98, www.lungusa.org/press/tobacco/prenatexpo.html.

Cornelius, Marie, et al, Prenatal tobacco effects on neuropsychological outcomes among preadolescents, Developmental and Behavioral Pediatrics, August, 2001, 22(4):217-224.

Brennan, Patricia, et al, Maternal smoking during pregnancy and adult male criminal outcomes, Archives of General Psychiatry, Mar., 1999, 56: 215-219, www.ama-assn.org/special/womh/library/readroom/arch99/yoa8114.htm. U.S. Surgeon General, Women and smoking: A report of the Surgeon General?2001, www.cdc.gov/tobacco/sgr/sgr_forwomen/ataglance.htm.

U.S. Public Health Service, Clinical Practice Guidelines: Treating Tobacco Use and Dependence, June, 2000, http://hstat.nlm.gov/tempfiles/is/tempBrPg62045.html

Campaign for Tobacco-Free Kids, Harm caused by pregnant women smoking or being exposed to second-hand smoke.

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