Smoking during pregnancy ups kids’ asthma risk: Study

Children with severe asthma are 3.6 times more likely to have been exposed to tobacco smoking before birth than children with a mild form of the disease, according to a new study.

The prenatal exposure also was associated with three times the number of daily and night-time asthma symptoms later in the child’s life, as well as nearly four times the number of asthma-related emergency room visits, the report said.

The prenatal impact far outweighed the role of exposure to cigarette smoke during the first two years of life, or current exposure to smoke, the study found.

This research team, which spanned 16 institutes and centers in the continental United States, Puerto Rico and Mexico, set out to determine when that exposure has the greatest impact, before birth, in the first two years, or at the time of the child’s symptoms.

They assessed 295 children with asthma, aged 8 to 16 years, from an existing study group of participants with Mexican, Puerto Rican and African American heritage.

“The only outcome that had an impact on the severity of asthma was smoking during pregnancy,” said Haig Tcheurekdjian, MD, a professor at Case Western Reserve University who was the co-senior author on the paper with UCSF’s Esteban Burchard, MD, MPH.

“Even after controlling for all of the other co-factors, the children who had the most severe forms of asthma were more than three times more likely to have had a mother who smoked while she was pregnant,” he added.

Smoking during pregnancy has previously has previously also been linked to asthma, the researchers said, but why prenatal exposure would affect the child’s lungs is unclear, since they’re not inhaling the smoke.

Researchers have speculated that this involved a genetic predisposition to lung inflammation, impaired lung development or the negative effects of tobacco smoke.

The current study points to genetic changes that occur long before a child takes its first breath.

“There are environmental factors that leave their fingerprint on DNA and may have their expression several years out,” explained Burchard, a UCSF clinical professor of Bioengineering and Therapeutic Sciences and Medicine who studies asthma genetics.

The study will be published in the journal Pediatrics.