SMOKING DURING PREGNANCY Pregnancy Risks and Socio-demographic Characteristics among Pregnant Smokers Sven Cnattingius University Hospital, Uppsala
Abstract Maternal smoking during pregnancy is causally related to fetal growth retardation. Smoking more than doubles the risk for the birth of a small-for-gestational-age infant. About 30% of the Swedish pregnant population smoke in early pregnancy. Despite that practically all pregnant women in Sweden today are aware of the hazards of smoking, about 70% of the smokers continue to smoke during pregnancy. Women who continue to smoke during pregnancy differ in terms of socio-demographic characteristics from those who stop smoking during pregnancy.
During the last three decades, antenatal care has more and more focused on fetal wellbeing and increased attention has been devoted to risk factors for an unsuccessful pregnancy outcome. Today, substantial evidence has been achieved that smoking is harmful for the mother and fetus during pregnancy. Smoking is also prevalent in the pregnant population. It has been suggested that smoking in Sweden may be the single most important risk factor for an unsuccessful pregnancy outcome, which at least theoretically, can be prevented (3;5). For obvious reasons, anything that harms the mother during pregnancy may potentially also harm the fetus. Consequently, simple classification of the potential smokingrelated risks during pregnancy into maternal and fetal risks are difficult. In the present presentation, maternal risks mainly concern those variables derived from measurements upon the mother. Risks associated with pregnancy outcome concern variables derived from measurements upon the infant. MATERNAL RISKS
In a review of publications from 1957 to 1979, Mclntosh (12) estimated relative risks (RR) for 28 events associated with pregnancy. In many studies, smoking was reported to be associated with pregnancy bleedings. As shown in Table 1, the relative risk for different causes of bleedings ranged from 1.2 (spontaneous abortions) to 1.7 (placenta praevia). Although these risk increases may be considered as modest, they are from The investigation of smoking habits during pregnancy was supported by grants from the Bank of Sweden's Tercentenary Fund and The Swedish Tobacco Company. 91
Cnattingius Table 1 . Smoking and Maternal Risk
Spontaneous abortion Placenta praevia Abruptio placenta Premature rupture of the membranes
Smoking during pregnancy. Pregnancy risks and socio-demographic characteristics among pregnant smokers.
Maternal smoking during pregnancy is causally related to fetal growth retardation. Smoking more than doubles the risk for the birth of a small-for-ges...