London: Children whose mothers smoked while pregnant are 65 per cent more likely to develop asthma, a new study has found.
Researchers from Karolinska Institute in Stockholm, Sweden, found that the risk of wheeze and asthma dramatically increased for those exposed to maternal smoking during pregnancy, the Daily Mail reported.
Wheeze is a continuous whistling sound during breathing caused by a narrowing of part of the respiratory tract.
The study included 21,600 children who came from eight birth cohorts across Europe.
Exposure to cigarettes and information on symptoms of wheeze and asthma were derived from questionnaires sent to the parents.
The analyses found children aged four to six who were exposed to smoking in the womb were 39 per cent more likely to have wheeze and 65 per cent more likely to have asthma.
Moreover, maternal smoking during the first three months of pregnancy, but not the last three or the first year following birth, was associated with increased risks for both conditions.
"The likelihood of developing wheeze and asthma increased in a significant dose-response pattern in relation to maternal cigarette consumption during the first three months of pregnancy," Dr Asa Neuman, one of the researchers said.
The risk rose even among children who were not exposed to maternal smoking late in pregnancy or after birth.
"These results indicate the harmful effects of maternal smoking on the foetal respiratory system begin early in pregnancy, perhaps before the woman is even aware she is pregnant," Neuman was quoted as saying by the paper.
"Our large pooled analysis confirms maternal smoking during pregnancy, particularly during the first three months, is associated with a greater risk of offspring developing wheeze and asthma when they reach preschool age.
The study was published in the American Journal of Respiratory and Critical Care Medicine.