Smoking in late pregnancy is linked to lower IQ in offspring
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《英国医生杂志》
Mothers who smoke in late pregnancy risk having children with lower intelligence. Young men whose mothers smoked 20 or more cigarettes a day had IQs that were on average 6.2 points below those of sons of non-smokers, research has found (Paediatric and Perinatal Epidemiology 2005;19:4-11).
The more cigarettes a woman smoked, the greater the risk. The association was as strong in children with high social status as in low status offspring.
"Our results reveal significant long term effects of maternal smoking during pregnancy on mental development. Maternal smoking during pregnancy was associated with lower adult intelligence and there appeared to be a dose-response relationship between maternal smoking and offspring intelligence," said authors Erik Mortensen and colleagues.
They say the findings may explain why smoking during pregnancy has also been linked to behavioural problems and increased risk of criminality in offspring.
In the research, the authors from Copenhagen University Hospital, Indiana University, and other institutions, used the Copenhagen perinatal cohort born between 1959 and 1961, which includes data on smoking in pregnancy, especially in the third trimester.
About half of the mothers were smokers, and, at the time the cohort was set up, Danish women were not being warned against smoking.
The authors then looked at intelligence data for 3044 of the sons, whose IQs were measured by military draft board intelligence tests at the age of 18 to 19.
The authors calculated the average IQ test results for five levels of smoking categories, adjusted for parental social status, breadwinner抯 education, single mother status, mother抯 height and age, number of pregnancies, and gestational age. A separate analysis took birth weight and birth length into account.
Maternal smoking during the third trimester, adjusted for the seven covariates, showed a negative association with offspring adult intelligence (P=0.0001). The mean difference between the non-smoking and the heaviest smoking category amounted to 0.41 standard deviations, corresponding to an IQ difference of 6.2 points.
The mechanism involved is not clear, but the authors say an adverse effect on the central nervous system and brain may be a factor: "It seems justified to assume that part of the effect of maternal smoking on offspring cognitive development is a direct result of the effect of substances in cigarette smoke on the fetal central nervous system."
"More specifically, maternal smoking may reduce uteroplacental circulation and cause fetal hypoxia which may particularly affect the development of the brain and thus subsequent intellectual development."(Abergavenny Roger Dobson)
The more cigarettes a woman smoked, the greater the risk. The association was as strong in children with high social status as in low status offspring.
"Our results reveal significant long term effects of maternal smoking during pregnancy on mental development. Maternal smoking during pregnancy was associated with lower adult intelligence and there appeared to be a dose-response relationship between maternal smoking and offspring intelligence," said authors Erik Mortensen and colleagues.
They say the findings may explain why smoking during pregnancy has also been linked to behavioural problems and increased risk of criminality in offspring.
In the research, the authors from Copenhagen University Hospital, Indiana University, and other institutions, used the Copenhagen perinatal cohort born between 1959 and 1961, which includes data on smoking in pregnancy, especially in the third trimester.
About half of the mothers were smokers, and, at the time the cohort was set up, Danish women were not being warned against smoking.
The authors then looked at intelligence data for 3044 of the sons, whose IQs were measured by military draft board intelligence tests at the age of 18 to 19.
The authors calculated the average IQ test results for five levels of smoking categories, adjusted for parental social status, breadwinner抯 education, single mother status, mother抯 height and age, number of pregnancies, and gestational age. A separate analysis took birth weight and birth length into account.
Maternal smoking during the third trimester, adjusted for the seven covariates, showed a negative association with offspring adult intelligence (P=0.0001). The mean difference between the non-smoking and the heaviest smoking category amounted to 0.41 standard deviations, corresponding to an IQ difference of 6.2 points.
The mechanism involved is not clear, but the authors say an adverse effect on the central nervous system and brain may be a factor: "It seems justified to assume that part of the effect of maternal smoking on offspring cognitive development is a direct result of the effect of substances in cigarette smoke on the fetal central nervous system."
"More specifically, maternal smoking may reduce uteroplacental circulation and cause fetal hypoxia which may particularly affect the development of the brain and thus subsequent intellectual development."(Abergavenny Roger Dobson)