Materials and Methods: The descriptive cross-sectional design was conducted at The Antenatal Clinic of the Out-patient Department of Obstetrics and Gynecology, Siriraj Hospital, Mahidol University. Three hundred pregnant women voluntarily answered the questionnaires. Duration of data collection was between August 18 and September 5, 2012.

Results: The mean age of women was 25.7±5.9 years. Over three-quarters of them worked outside home, 4.3% of women had ever smoked, and 1% of them continued smoking during pregnancy. Nearly all women were aware of the harms of cigarette smoking to their health and were positive to the anti-cigarette smoking campaign.

Conclusion: Pregnant women possessed high knowledge of the harms of tobacco smoking, but did not have a clear image of second hand smokers. The anti-smoking campaign particularly via the television is very useful for public awareness.

Keywords: Cigarette smoking, Pregnant women, Knowledge, Attitude