Cord Serum Cotinine as a Biomarker of Fetal Exposure to Cigarette Smoke at the End of Pregnancy
Pichini, Simona, Basagana, Xavier, Pacifici, Roberta, Garcia, Oscar, Puig, Carmen, Vall, Oriol, Harris, Jessica, Zuccaro, Piergiorgio, Segura, Jordi, Sunyer, Jordi, Environmental Health Perspectives
This study investigated the association between biomarkers of fetal exposure to cigarette smoke at the end of pregnancy, cotinine in cord serum and in maternal and newborn urine samples, and quantitative measurement of smoking intake and exposure evaluated by maternal self-reported questionnaire. Study subjects were 429 mothers and their newborns from a hospital in Barcelona, Spain. A questionnaire including smoking habits was completed in the third trimester of pregnancy and on the day of delivery. Cotinine concentration in cord serum was associated with daily exposure to nicotine in nonsmokers and with daily nicotine intake in smokers. The geometric mean of cotinine concentration in cord serum statistically discriminated between newborns from nonexposed and exposed nonsmoking mothers, and between these two classes and smokers, and furthermore was able to differentiate levels of exposure to tobacco smoke and levels of intake stratified in tertiles. Urinary cotinine levels in newborns from nonsmoking mothers exposed to more than 4 mg nicotine daily were statistically different from levels in two other categories of exposure. Cotinine concentration in urine from newborns and from mothers did not differentiate between exposure and nonexposure to environmental tobacco smoke (ETS) in nonsmoking mothers. Cord serum cotinine appeared to be the most adequate biomarker of fetal exposure to smoking at the end of pregnancy, distinguishing not only active smoking from passive smoking, but also exposure to ETS from nonexposure. Key words: cord blood, cotinine, daily exposure to nicotine, fetal exposure to cigarette smoke, nicotine daily intake, questionnaire, urine. Environ Health Perspect 108:1079-1083 (2000). [Online 25 October 2000]
Prenatal exposure to smoking has consequences both in childhood and in adulthood (1-5). Fetal exposure to cigarette smoke is usually assessed by questionnaires administered to mothers during or after pregnancy (1,6). However, difficulties in recognizing smoking behavior or recalling smoking exposure, or changes in smoking habits during gestation could bias these assessments.
In a country such as Spain, with a high prevalence of young female smokers(7) and a high passive intake through social events (8), questionnaires could be even less valid. In addition, pregnant women, conscious of the risks of tobacco smoke products for the fetus, may be reluctant to admit active smoking or passive exposure due to social pressure(9).
In recent years there has been increasing interest in the use of biomarkers of smoking exposure to improve the validity of assessment by questionnaire(9-13). At present, cotinine measured in blood, saliva, or urine appears to be a reliable marker of recent smoking status in population studies (14-16). However, collection of saliva or urine in newborns is rather unfeasible.
Two recent studies have measured cotinine in cord blood(9, 11) and compared it to self-reported maternal smoking. The first study(9) included 27 newborns from smoking mothers, whereas the other study(11) was carried out in a population with a low intensity of smoking during pregnancy and without measurement of exposure to environmental tobacco smoke (ETS).
Within the framework of a cohort study on the effects of prenatal and postnatal environmental exposures in the inception of atopy and asthma [Asthma Multicenter Infant Cohort Study; AMICS(17)], we aimed to measure prenatal exposure to tobacco smoke. For this purpose, cotinine was measured in cord serum samples and maternal and newborn urine collected on the day of delivery and compared to maternal self-reported questionnaires. The objective of the present analysis was to assess the association between these biomarkers of exposure, particularly cotinine in cord blood, and the quantitative measurement of smoking intake and exposure at the end of pregnancy measured through questionnaire. …