Moms' Smoking May Lead to Baby's Asthma
THURSDAY, Feb. 15 (HealthScout) -- If you're pregnant and smoking, you're smoking for two, and your baby may develop the asthma to prove it, suggests new research.
And, the child's asthma will get worse if it's exposed to more tobacco smoke after birth, say the researchers.
It's no secret that tobacco smoke is bad for children diagnosed with asthma; it triggers more symptoms and requires more drugs and trips to the emergency room.
But until now, it's been hard to separate the two phases of smoke exposure: before birth and when breathing secondhand smoke after birth. Researchers from the University of Southern California in Los Angeles reveal the impact of each type of exposure in the February issue of the American Journal of Respiratory and Critical Care Medicine.
Lead investigator Dr. Frank Gilliland, an associate professor of preventive medicine, studied how tobacco smoke exposure affected children early in life with data from the 10-year Children's Health Study, a long-term follow-up of 5,762 children from 12 Southern California communities. Gilliland and his team analyzed questionnaires filled out by the children's parents about each child's lifetime tobacco exposure, including whether the mother smoked during pregnancy, as well as information about whether the child wheezed or had been diagnosed with asthma.
They found 18.8 percent of the children were exposed to smoke while in the womb, and 39.5 had some lifetime exposure to environmental tobacco smoke (ETS). Of the children exposed in the womb, 17.8 percent were told by doctors they had asthma, while 38.3 percent of those with later exposure to smoke had a history of wheezing.
"What we found was that exposure during the in utero period was very important for subsequent development of asthma, as well as the severity of asthma later on," says Gilliland. "Environmental tobacco smoke added to that. If you were exposed both as a fetus in the womb and later in life, then you got a double whammy."
The researchers don't completely understand what effects the mother's smoking has on the developing lungs of a fetus. "We do know that it causes smaller lungs; it causes the small airways to be abnormal," says Gilliland. "One possible explanation is the airways [in general] are much smaller. They also appear to be much more responsive to insults, and that makes [the children exposed in utero] more likely to have asthma."
Dr. Jonathan Samet, chairman of the Department of Epidemiology at Johns Hopkins University in Baltimore, Md., says other studies have shown that ETS can affect lung growth, increase risk for respiratory infection, make children more likely to cough or wheeze and possibly increase the risk for asthma.
"This is another piece of evidence consistent with the idea that mom's smoking during pregnancy increases the risk for asthma, and it's clearly a lot of evidence that smoke exposure anytime increases risk for symptomatic wheezing," says Samet.
"One of the difficult questions has been trying to sort out how much of that represents an effect of smoke exposure after birth versus some carry-over effects from exposure during pregnancy. This study attempts to get at that," he says.
What To Do
Gilliland says the challenge will be to motivate people to act. "We know that parents need to quit smoking, not only after the kids are diagnosed with asthma. But, if a child has been exposed in utero to maternal smoking, then it's really imperative that the parents don't smoke around the child."
"I'd like to see a renewed effort to make sure that young women don't start smoking, and if they have, to quit before they start having their family, because that has the potential to prevent a lot of asthma cases," says Gilliland. "Unfortunately, we have a lot of young women who are smoking for various reasons now, more so than in the past, and it doesn't bode well for their kids."
Gilliland and his colleagues are working on new study to see if the amount an expectant mother smokes affects the likelihood of her child developing asthma.