OBJECTIVELY MEASURED TOBACCO EXPOSURE AMONG PREGNANT-WOMEN IN FINLANDIN 1986 AND 1990

Objective. First, to study tobacco exposure among pregnant Finnish wom en in 1986 and 1990. Second, to study the objectively measured exposur e in different socioeconomic classes and in different geographical reg ions. Third, to assess the value of serum thiocyanate concentrations i n estimating fetal tobacco exposure. Design. Tobacco exposure was meas ured from maternal and umbilical serum samples by measuring the concen tration of nicotine metabolite, cotinine. In addition, the concentrati ons of thiocyanate were measured from umbilical serum samples. The occ upations of the mothers were obtained from the Finnish Birth Registry, and the area of residence from laboratory records. Setting. Finland. Subjects. 1323 infants born in late February-early March in 1991, 1263 mothers of these infants during antenatal visits in Autumn 1990, and 976 pregnant mothers during antenatal visits in Autumn 1986. The mothe rs and infants studied represented all newborn infants and their mothe rs during one week in one country. Measurements and main results. In 1 986, 21.3% of Finnish mothers and in 1990 21.2% were exposed to tobacc o. In 1986, exposed mothers were on average 1.4 (95% confidence interv al 0.9-1.8) years younger than nonexposed mothers, and in 1990, expose d mothers were on average 1.6 years (95% confidence interval 1.1-2.3) younger than nonexposed mothers. 28.5% of mothers classified as unskil led workers were exposed, but only 9.1% of those classified as upper w hite-collar. There were no significant geographical differences in exp osure. Although umbilical serum thiocyanate levels were always elevate d in exposed infants, high serum thiocyanate concentrations were detec ted in infants not exposed to tobacco. Conclusions. More than 20% of p regnant Finnish mothers and their fetuses were exposed to tobacco in 1 986 and 1990. Young women and women in low socioeconomic classes were the most seriously exposed. Measurement of serum thiocyanate concentra tions did not yield reliable estimates of exposure.