Background Stress is a complex condition that can have a profound effect on an individual’s sense of wellbeing and their ability to live a happy and healthy life. COVID-19 and its associated stressors have the potential to disrupt numerous facets of our everyday lives. Pregnant and postpartum women are especially vulnerable to changes in the availability of routine health and social care services and of their support networks. The current study sought to explore stress levels and their influencers among an international cohort of pregnant and postpartum women during the COVID-19 pandemic. Methods We conducted an anonymous, online, cross-sectional survey in 64 countries between May and June 2020. The survey was hosted on the Pregistry platform and made available in 12 languages, with respondents sought through a variety of social media platforms and parenting forums. In addition to levels of stress, we collected data related to demographics, COVID-19 exposure and worries, lifestyle changes, traditional and social media use, precautionary measures related to COVID-19, and mental health. Results In total, 7185 women were included in our sample. We found statistically significant (p-value <0.05) reductions in stress score among older women (≥35 years of age), those either living with a partner or married, those who had graduated from college, and those with medical coverage. Higher stress scores were found among women who resided in Africa, Asia and the Pacific, the Middle East, and North America compared with those in Europe. When race and ethnicity were included in the model, black women were found to have higher stress compared to white women. Level of family and community support was inversely associated with level of stress. Conclusion Our study is one of the first to explore stress levels among pregnant and postpartum women during the COVID-19 pandemic. We found statistically significant differences in stress levels by age, education, marital status, region of residence, race/ethnicity and level of support. Understanding stress during the COVID-19 pandemic, and exploring ways to address it, will be key to contributing to the mental and physical health of expectant and new mothers, as well as their children, in both the short and long term.