The aim of the study was to estimate both active and passive pregnant women exposure to tobacco smoke. 154 women hospitalized at the Gynaecology and Obstetrics Department in Opole, Poland and at the Gynaecology and Obstetrics Department of Hospital Universitario Monterey in Mexico have undergone the examination. The patients have been surveyed in order to obtain a subjective evaluation of their exposure. Then the exhaled carbon monoxide (ExhCO) measurement used for objective monitoring tobacco smoking has been performed. According to the results of the questionnaire 40 women (26% of the examined patients) confirmed smoking in pregnancy. 24 women (60% of smoking ones) have been smoking for the whole period of pregnancy. Though the rate of smoking among Polish and Mexican women was comparable, Polish mothers were less likely to quit after confirmation of pregnancy. Both Polish and Mexican smoking mothers were much younger than their non-smoking counterparts. The babies of the smoking mothers have been noticed to obtain the lower count in Apgar scale. The exhaled carbon monoxide (ExhCO) measurement has revealed that 14 Polish and 10 Mexican patients have been exposed to tobacco smoke. The results of their questionnaires have been thoroughly examined. 71% of them confirmed active smoking in pregnancy, 8.3% pointed to second-hand smoke exposure, 20.7% lied by denying the exposure. Thus the need to verify the questionnaires results has been confirmed. The mean value of ExhCO of both non-smoking women and those, who quit smoking after confirmation of pregnancy was equal. This may suggest that quitting smoking in the early stages of pregnancy reduce the risk of the harmful smoke impact on the unborn baby. Nearly doubled average concentration of ExhCO among passive smoking mothers in comparison to the non-smoking ones arises a serious concern.