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19-08-2012 | General practice | Article

Early pregnancy smoking risks asthma



medwireNews: Children are more likely to develop wheeze and asthma at an early age if their mother smoked during the early stages of pregnancy, Swedish researchers report.

The risk of wheeze and asthma is increased even if a mother quits later on in pregnancy or after birth, says the team from Karolinska Institutet.

"These results indicate that the harmful effects of maternal smoking on the foetal respiratory system begin early in pregnancy, perhaps before the woman is even aware that she is pregnant," lead author Dr Åsa Neuman explained in a press statement.

The analysis of eight birth cohorts included 21,600 children, 735 of whom were exposed to maternal smoking only during pregnancy. After adjusting for sex, parental education, parental asthma, birthweight and siblings, maternal smoking during pregnancy only was associated with a 1.4-fold increased risk of wheeze and a 1.7-fold increased risk of asthma at age 4-6 years.

Further analysis showed that the increased risks of both wheeze and asthma were seen for women who smoked in the first trimester but not during the third trimester or the first year following birth.

The findings are published in the American Journal of Respiratory and Critical Care Medicine.

"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," Dr Neuman commented.

MedWire ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2012

By Caroline Price