URINARY COTININE AS A MEASURE OF TOBACCO SMOKE EXPOSURE IN UTERO AND INFANCY

Maternal smoking during pregnancy and after birth has adverse effects on infants. However, studies to date have not used quantitative measures of infant tobacco smoke exposure. A RIA for cotinine, the major metabolite of nicotine, has been used for this purpose in adults. We studied whether urine cotinine could be detected in exposed newborns and young infants. Urine was collected every 12 hrs for the first 5 days of life from 7 newborns of smoking mothers and 1 control, all isolated from tobacco smoke after birth. Initial mean cotinine/creatinine in exposed newborns was 1884 ng/mg (range 364 to 3888 ng/mg); these are comparable to values found in non-smoking adults with workplace tobacco smoke exposure. The control infant had only 18 ng/mg. Cotinine elimination halftime was 56 hrs, more than twice that seen in adults. Urine cotinine was measured in 18 non-hospitalized, non-exposed infants and in 28 infants with at least 2 recent exposures. Mean cotinine/creatine from exposed infants was significantly greater (p<0.0001) than from non-exposed (459 vs 19 ng/mg), with a direct relationship between cotinine excretion and number of cigarettes consumed daily by the mother (r=0.64, p=0.0001). Urine cotinine is an easily obtainable and reliable measure of infant tobacco smoke exposure.