Background: As the pandemic of COVID-19 is still present up to now, major concerns are being raised up about its effects on pregnancy and the potential risks of vertical transmission from the pregnant women to their fetuses. Aim: the present study aim to assess pregnant women's concerns about Coronavirus disease 2019 (COVID-19) and its relationship to their preventive behaviors. Subjects and methods: design: A descriptive cross-sectional research design was used in this study. Setting: The study was conducted at obstetric and gynecological outpatient clinics at Tanta University hospital. Sampling: A convenient sample of 284 pregnant women. Tools of data collection: Three tools were used for data collection. Tool I consisted of three parts, part I: Socio-demographic characteristics, Part II: Obstetric history, Part III: Women's Knowledge about Corona Virus, Tool II: Pregnant Women's Concerns about Corona Virus and Tool III: Pregnant Women's Preventive Behaviors regarding Corona Virus. Results: the results of the present study revealed that (55.3%) had high knowledge level, (70.4%) had high concerns about COVID-19 pandemic respectively, and (52.8 %) of studied pregnant women's had satisfactory preventive behaviors against covid-19 virus. Conclusion: Based on the findings of the present study, it can be concluded that pregnant women's level of knowledge and concerns significantly correlated to their compliance with recommended preventive behaviors regarding COVID-19.  Recommendation: The current study suggested that maternity nurses should pay more attention and reach to the lower-educated younger pregnant women especially in rural areas being a group with the least engagement in health preventive behaviors.