Editor,—In 1994, women matched men with regard to smoking rates in Spain. In 1996, rates of daily smoking at 17 years of age showed a clear transition from men (24%) to women (29%). These figures rose to 43% and 45% in men and women, respectively, at 24 years of age during 1998 in a Spanish Health Interview Survey.1 This high incidence of tobacco consumption in young women in Spain may have unfavourable effects on the health of new generations exposed to maternal smoking and environmental tobacco smoke since gestation.

We assessed the recent in utero exposure to tobacco smoke in newborns from the Barcelona cohort of the AMICS study (Asthma Multicentre Infants Cohort Study). Pregnant women (n = 500, median age = 29 years) attending the Hospital del Mar in Barcelona (the fourth biggest hospital in the city) during 1997–1998 were invited to participate if expecting to live in Barcelona the forthcoming years and in possession of a telephone number. A questionnaire including smoking habits was completed in the third trimester of pregnancy and on the day of delivery. Cotinine, the major nicotine metabolite, was assayed in cord serum using a radioimmune assay technique with a detection limit of 0.2 ng/ml in 409 newborns. Cotinine in cord serum was chosen because it is a highly sensitive and specific biomarker of recent smoking status in population studies, and cannot indicate exposures other than smoking.2

One hundred and thirty four mothers (33%) reported daily smoking during the last trimester of pregnancy. Questionnaire was confirmed by a 34% of cord blood samples having cotinine concentration above 14 ng/ml, the cut off point established to separate between daily smokers and non-smokers.3 This prevalence of active smoking during pregnancy is noticeably higher than in many European countries,3 4 or USA.5 Furthermore, of the remaining 275 cord blood samples coming from non-smoker mothers reporting both exposure and non-exposure to environmental smoke during pregnancy, 83% presented cotinine levels above 1 ng/ml, a cut off used to distinguish exposure from no exposure to environmental tobacco smoke.2 This finding indicates a universal fetal exposure to cigarette smoke at least during the last days of pregnancy. The importance of non-parental sources in passive exposure to cigarette smoke by infants was recently evidenced despite commonly underreporting or unawareness of this phenomenon to underline the question of smoking epidemic affecting children.6

Although our cohort was not randomly selected, the coincidence of prevalence of smoking with the more recent general interview survey (45% between 15 to 24 years of age in both), as well as the coincidence of social class distribution based on mother occupations, suggests that these findings could be representative of the whole city. We conclude that in Barcelona it is almost impossible not to be exposed to cigarette smoke even during last days of pregnancy. The smoking epidemic in Barcelona is a paradigm of the smoking transition from men to women, which has appeared recently in Spain and is going to appear in other countries, with its harmful consequences in future generations.