MONDAY, Aug. 13, 2001 (HealthDayNews) -- If you're pregnant and smoke, you double your chance of losing your baby. But if you can quit smoking in your first trimester, that risk gets wiped out completely, a new Danish study says.
Researchers found that exposure to tobacco smoke in the womb doubled the risk of stillbirth, and that the infant mortality rate for smokers was 1.8 times greater than for nonsmokers.
But, the researchers say, women who gave up the habit in the first trimester had the same rates for stillbirth and infant mortality as women who never touched a cigarette during their pregnancy.
Dr. Kirsten Wisborg, a professor of gynecology and obstetrics at Aarhus University in Denmark, led a team that followed 25,000 pregnant women. "Our focus has been on lifestyle," she says in an e-mail interview, "that is, smoking, alcohol and caffeine intake."
Wisborg and her colleagues did three sets of interviews with all the pregnant women scheduled to give birth at Aarhus University Hospital, in Aarhus, Denmark, between 1989 and 1996. About 70 percent were nonsmokers. Among the smokers, 44 percent smoked less than 10 cigarettes a day, Wisborg says.
"What we found was that smoking during pregnancy increases the risk of stillbirth and infant mortality," Wisborg says. "The risk is doubled in children born to smokers, compared to children of nonsmokers."
But she says, if a pregnant women stops smoking in the beginning of her pregnancy, the risk of stillbirth and infant death is reduced to the risk found in nonsmokers.
That risk, she adds, " is not explained by other factors such as maternal age, alcohol intake, or socioeconomic status."
The study concludes that -- with a smoking rate of 30 percent -- 25 percent of all stillbirths and 20 percent of all infant deaths in a population could be avoided if all pregnant smokers stopped smoking by the 16th week of pregnancy.
The findings appear in the Aug. 15 issue of the American Journal of Epidemiology.
When a pregnant woman smokes, two of the major toxins from cigarette smoke -- nicotine and carbon monoxide -- pass through the placenta to the fetus, according to the U.S. Centers for Disease Control and Prevention. This can cause pregnancy complications, premature birth, and low birth weight. Smoking mothers also put their infants at risk for sudden infant death syndrome (SIDS), poor lung development, asthma and respiratory infections.
The CDC estimates that perhaps as much as 30 percent of women of reproductive age -- 14 million women between 18 and 44 years old -- still smoke.
Wisborg says the study only looked at statistics, and she cannot explain why quitting smoking during the first trimester caused no further problems.
Nevertheless, her message is, don't smoke if you plan to get pregnant.
"Every cigarette counts," she says. "Stop smoking before you get pregnant and, if needed, use a nicotine substitution. And if you can't stop smoking, reduce the number of cigarettes you smoke as much as possible."
"You shouldn't interpret this study to mean that there's no risk in smoking during the first trimester," adds Dr. Norman Edelman, president of the American Lung Association. "People need to remember that smokers have smaller babies, those babies have smaller lungs, and they are more likely to develop asthma. Nobody knows when that damage takes place."
Edelman adds: "The real message, as it always has been, is if you contemplate getting pregnant, stop smoking."
"Smoking reduces blood flow to the placenta, so what we're seeing in this study is that if you continue to smoke after the first trimester, that's likely impacting the placenta and leading to stillborn birth," he says.
What To Do
For more information on pregnancy and smoking, see the Centers for Disease Control and Prevention and the American Lung Association.
