Smoking During Pregnancy Increases Kid's Asthma Risk

Variation of enzyme makes some children especially vulnerable to breathing problems

FRIDAY, Aug. 16, 2002 (HealthDayNews) -- Children whose mothers smoked during pregnancy have an increased chance of getting asthma if they don't have a certain type of enzyme.

The enzyme also exists as a variation, and the variation is so common in children that it affects the ability of the lungs to protect themselves, according to a study in the latest edition of the American Journal of Respiratory and Critical Care Medicine. And if mothers were smoking while they were pregnant, their children were more susceptible to asthma and other respiratory illnesses, the researchers conclude.

The variation involves a gene called glutathione S-transferase M1 (GSTM1), which creates an enzyme that helps the lungs protect themselves from pollutants. The enzyme detoxifies some tobacco pollutants and defuses oxidants before they can damage lung tissue.

Children with the GSTM1 null genotype who were exposed to cigarette smoke while in the womb were much more likely to have asthma, wheezing and breathing-related emergency room visits compared to children with the GSTM1 present genotype, the study says.

Researchers at the Keck School of Medicine at the University of Southern California studied 2,950 children in grades 4, 7 and 10. Their parents were asked about whether the mother smoked when she was pregnant, and whether their kids had suffered breathing problems.

More than 16 percent of the children had mothers who smoked during pregnancy, and more than 45 percent of the children had the GSTM1 null genotype.

When the researchers looked at the children with the null genotype whose mother smoked during pregnancy they found:

  • Almost a four-fold increased risk for emergency room visits within the past year.
  • More than a double risk for wheezing with exercise and wheezing requiring medication.
  • An 80 percent increased risk for a lifetime history of wheezing.
  • 70 percent and 60 percent increased risks for asthma with current symptoms and early onset, asthma, respectively.

There was no increased risk for respiratory problems in children with the GSTM1 present genotype who were exposed to cigarette smoke in the womb.

"Findings show that exposure to smoke in the womb for certain genetically susceptible children may have long-term health effects," says study author Dr. Frank D. Gilliland, professor of preventive medicine.

"Maternal smoking is common, and the null genotype is found in nearly half of the population, so this high-risk group might be an important population to target for prevention," he says.

More information

Nicotine addition is one of the hardest habits to kick. But if ever there was reason to quit, pregnancy has to be at the top of the list.

This useful question-and-answer page from the American Lung Association explains the risks a woman runs by continuing to smoke during pregnancy.

SOURCE: University of Southern California news release, Aug. 16, 2002
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