Updated 02 August 2017

Prenatal smoking tied to worse asthma in kids

Children whose mothers smoked during pregnancy may have a tougher time controlling their asthma, a new study suggests.

Children whose mothers smoked during pregnancy may have a tougher time controlling their asthma, a new study suggests.

The findings, from a study of nearly 2 500 US kids, offers more motivation for doctors to ask moms and expectant moms about smoking, said lead researcher Sam Oh, of the University of California San Francisco.

"Pregnancy is a great opportunity for smoking cessation," he said.

How the study was done

For their study, the researchers focused on 2 481 black and Hispanic kids between the ages of eight and 17 who all had asthma and were mostly from low-income families.

In the US, poor, minority children are at particular risk of asthma. About 16% of low-income black children have asthma, whereas the national prevalence is 9%, according to the US Centres for Disease Control and Prevention.

In this study, almost 19% of African-American moms smoked at some point during pregnancy, as did 5.5% of Hispanic moms.

Overall, their kids were at greater risk of poor asthma control later in life, even when childhood secondhand-smoke exposure was taken into account – as well as other factors like a child's age and asthma medication use.

About 30% of Hispanic kids and 38% of black kids had poorly controlled asthma symptoms – and the risk was 50% for those exposed to smoking in utero, vs unexposed kids.

"There are measurable effects even years down the road," Oh said.

Tobacco impairs lung development

The findings do not, however, prove that prenatal smoking, itself, causes more-severe asthma symptoms later in life. They can only point to a correlation. But there is lab research, in animals and human cells, suggesting there could be a direct effect, Oh pointed out.

Foetal exposure to tobacco smoke may, for example, impair early lung development, or have lasting effects on the activity of certain genes.

The bottom line, according to Oh, is that there is already a host of reasons for pregnant women to quit smoking for good, and this may be one more.

Behavioural counselling can help

 "This study provides more impetus for healthcare providers to ask about smoking at each visit," he said.

Some pregnant women may be able to quit with behavioural counselling. In nicotine replacement therapy or other medication can be used.

The study was published online  in the Journal of Allergy and Clinical Immunology.

(Amy Norton, Reuters Health, May 2012) 

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Professor Keertan Dheda has received of several prestigious awards including the 2014 Oppenheimer Award, and has published over 160 peer-reviewed papers and holds 3 patents related to new TB diagnostic or infection control technologies. He serves on the editorial board of the journals PLoS One, the International Journal of Tuberculosis and Lung Disease, American Journal of Respiratory and Critical Medicine, Lancet Respiratory Diseases and Nature Scientific Reports, amongst others.Read his full biography at the University of Cape Town Lung Institute

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