Healthnotes Newswire (September 21, 2000)——Children born to mothers who smoke during pregnancy are more than three times as likely to die from the sudden infant death syndrome (SIDS), according to a study published in this month’s edition of the Archives of Diseases of Childhood.¹

In the new study, 25,000 Danish women filled out a questionnaire in the 16th and 30th weeks of pregnancy. Women who reported that they were currently smoking at least one cigarette per day, but not those who had quit smoking during the first 16 weeks of pregnancy, were considered smokers in the study. The children of the women enrolled in the study were followed for one year, and the incidence of SIDS was noted.

Children of women who smoked during pregnancy were found to be at three times the risk of SIDS compared with the children born to mothers who did not smoke. The risk of SIDS increased with the number of cigarettes smoked per day. Adjustment of the data for a number of other potentially important variables, including maternal weight, caffeine intake, and consumption of alcohol, did not change the results.

An association between maternal smoking and SIDS has also been found in other studies.^{2 3 4 5} The new study, however, was the first to ask women about smoking habits at the time they were pregnant and before the deaths of their infants. This makes the results less susceptible to bias, because studies that assess current behaviors (as opposed to previous behaviors) are less prone to errors in reporting.

It is possible that this study has underestimated the effect of smoking on the incidence of SIDS. If exposure to cigarette smoke in early pregnancy (before the 16th week) is also associated with increased SIDS risk, then the reported risk in this study may not reflect all of the cases that were due to smoking.

An alarming finding in this study was that 30% of the pregnant mothers who filled out the questionnaire reported that they were currently smoking. Such a high rate of smoking reflects a failure of public health warnings, at least in Denmark, to convince pregnant mothers of the dangers of cigarette smoking.

The authors of the new study concluded that 30–40% of all cases of SIDS could be prevented if the number of pregnant women who smoke can be reduced from 30% to zero. SIDS can be added to the list of other detrimental effects of maternal smoking during pregnancy, including increased risk of preterm delivery, fetal mortality, childhood cancers, childhood allergies, infantile febrile seizures, birth defects of the urinary tract, and lower IQ.⁶ Now, more than ever, it is of extreme importance that pregnant mothers be informed of the risks to an unborn child of smoking during pregnancy.