Smoking during pregnancy increases the risk of developing wheezing and asthma in preschool children.
Researchers from the Karolinska Institutet in Sweden have found that children, whose mothers had smoked during pregnancy, are at higher risk of developing wheezing and asthma.
"Epidemiological evidence suggests that exposure to maternal smoking during fetal andearly life increases the risk of childhood wheezing and asthma, but earlier studies were not able to differentiate the effects of prenatal and postnatal exposure," said Åsa Neuman, researcher at the Institute of Environmental Medicine at the Karolinska Institutet.
"These children were at increased risk for wheeze and asthma at preschool age. Furthermore, the likelihood of developing wheeze and asthma increased in a significant dose-response pattern in relation to maternal cigarette consumption during the first trimester."
The discovery was made while analysing the data of more than 21,000 children aged between four to six years, including 735 children were exposed to maternal smoking only during pregnancy from eight birth cohorts across Europe.
Researchers found out that smoking during pregnancy has a major impact on the child's health. They found that 39 percent of the children, who were exposed to smoking during pregnancy, are at a higher risk of developing wheezing and 65 percent of the children are at a higher risk of developing asthma.
The study also found that maternal smoking during the first trimester of pregnancy, but not during the third trimester or the first year following birth was associated with increased risks for subsequent wheezing and asthma, according to the findings published in the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine.
These results indicate that the harmful effects of maternal smoking on the fetal respiratory system begin early in pregnancy, perhaps before the woman is even aware that she is pregnant.
"Our large pooled analysis confirms that maternal smoking during pregnancy, particularly during the first trimester, is associated with a greater risk of offspring developing wheeze and asthma when they reach preschool age. Teens and young women should be encouraged to quit smoking before getting pregnant," concluded Dr Neuman.