Rational and Background: Pregnant women are more likely to be at risk of oral disease compared to those who are not pregnant. Oral disease during pregnancy affects not only maternal but also child health. Very little is known about the oral health problems among Lao pregnant women. Methodology: In this descriptive, cross-¬sectional study we described the oral health problems and identified factors related to the oral diseases among Lao women with > 12 weeks of pregnancy who visited the two central hospitals (Mother and Child Health and Mahosot) in Vientiane, Laos between January and February 2010. Oral health was checked by a dentist and an interview was conducted with pregnant women using pre¬designed questionnaires. Data were analyzed using STATA 8.0 and logistic regression was applied to determine factors associated with oral diseases. Results: Five hundred pregnant women aged between 15 and 42 years [Mean (SD) = 26.7 (5.0)] were studied. The proportion of oral disease was 64.6% [dental carries (43%), gingivitis (8.4%), and both carries + gingivitis (13.2%)]. Half of the pregnant women (52.8%) had poor oral health care (brush teeth < 2 times per day). Factors associated with oral disease were monthly income > 2,000,000 LAK/month [OR = 1.8, 95%CI = 1.0 ¬3.0, P = 0.04], teeth brushing < 2 times per day [OR = 2.0, 95%CI = 1.1 ¬3.7, P = 0.03], > 2 pregnancies in their lives [OR = 2.6, 95%CI = 6.0 ¬10.0, P < 0.001], those with > 2 deliveries in their lives [OR = 5.4, 95%CI = 1.2 ¬2.1, P < 0.001], and those with history of oral disease before pregnancy [OR = 2.5, 95%CI = 1.7 ¬3.8, P < 0.001]. Conclusion: This study showed that more than half of Lao pregnant women had oral disease and their oral health self¬-care behavior was low. Poor oral health self-¬care behavior, multiple pregnancies and deliveries, and history of oral disease before pregnancy were factors significantly related with oral disease during pregnancy. Health education on oral health self¬-care and oral health check during ante¬natal clinic visits by the pregnant women should be provided and urgently implemented.