Smoking in pregnancy has longer-term effects on children

Children whose mothers smoked during pregnancy have a higher risk of behavioural problems at age nine than those who abstained, research shows.

The findings, part of a longitudinal study called Growing Up in Ireland, show that the effects of maternal smoking when pregnant stretch well beyond premature birth and low birth weight.

Long-term, a child’s academic performance can also suffer where behavioural problems include an inability to settle down and pay attention, Dr Cathal McCrory, one of the study’s authors, said.

Significantly, the finding still stood when other factors such as the mother’s socio-economic status and mental wellbeing — which can affect whether and how heavily a person smokes — were stripped out.

“It was still really clear that smoking during pregnancy had an effect on a child’s behaviour, and the risk of behavioural problems increased with the number of cigarettes the mother smoked,” Dr McCrory said.

In fact, the heavier the smoker, the greater the impact. Children whose mothers smoked 11+ cigarettes a day during pregnancy were 78% more likely to be defined as having a behavioural problem than the children of non-smokers. This compares with 32% of children whose mothers were occasional smokers. While this study, published by the Economic and Social Research Institute (ESRI), looked at behaviour of children aged nine, a study in Britain found behavioural problems in children as young as three whose mothers smoked during pregnancy.

“There are a whole lot of toxic compounds in cigarettes which are believed to have toxic effects on brain development, some of which are evident at a really early age, such as increased irritability, heightened startle and tremors,” Dr McCrory said.

He said their findings reinforced the need for programmes aimed at promoting successful cessation of smoking during what is a critical period for the developing infant. The study also found the proportion of mothers who smoke during pregnancy has fallen from 28% in the late 1990s to 17.6% currently but that the level of smoking in pregnancy in Ireland is higher than in Northern Europe.

Growing Up in Ireland is a government-funded study following the progress of almost 20,000 children and families.

* www.growingup.ie