Objectives: The purpose of this study is to examine the effects of coronavirus disease 2019 pandemic on the prevalence of anxiety, depression, stress, insomnia, and social dysfunction among pregnant and/or lactating women and to measure the global pooled prevalence of mental health effects among these populations in the era of coronavirus disease 2019 pandemic. Methods: Comprehensive literature searching was conducted and studies published from 1 January 2020 to 30 September 2020 reporting the prevalence of anxiety, depression; stress, insomnia, and social dysfunctions were included. The pooled prevalence of anxiety, depression, stress, insomnia, and social dysfunctions was estimated using a random-effect model. In this study, all statistical analyses were performed using STATA (version 15) software. Results: There were a total of 19 studies included in the meta-analysis, of which 16, 14, 4, 2, and 2 studies were included in computing the pooled prevalence of anxiety, depression, stress, insomnia, and social dysfunction, respectively. The pooled prevalence of anxiety was 33% (95% confidence interval: 50%−61%), with significant heterogeneity between studies (I2 = 99.68%, p = 0.001). The pooled prevalence of depression was 27% (95% confidence interval: 9%−45%), with remarkable heterogeneity between studies (I2 = 99.29%, p = 0.001). Likewise, the pooled prevalence of stress was 56% (95% confidence interval: 30.07%−82.22%), with significant heterogeneity between studies (I2 = 98.8%, p = 0.0001). The pooled prevalence of social dysfunction was 24.3% (95% confidence interval: 13.41%−62.03%), with significant heterogeneity between studies (I2 = 97.5%, p = 0.0001) and finally, the pooled prevalence of insomnia was 33.53% (95% confidence interval: 3.05%−64.0%), with significant heterogeneity between studies (I2 = 99.6%, p = 0.0001). Conclusions: In this study, the mental health effects of the COVID-19 pandemic among pregnant and lactating women were found to be significant. Stress was the most common mental health problem in these population groups. Therefore, policymakers and health planners should give great emphasis to addressing maternal mental well-being during and after this global health crisis. Maternal mental health must be one of the international and national public health priority agendas to enhance the well-being of pregnant and lactating women. Besides, giving psychological support to pregnant and lactating women may reduce the long-term negative effects of this pandemic.