Background: Women during pregnancy and in the first year after childbirth are vulnerable to mental disorders in the outbreaks of infectious diseases such as Coronavirus Disease (COVID-19). There is a relationship between mental health and marital satisfaction. This study aimed to assess mental health, anxiety, depression, and marital satisfaction among pregnant and lactating women and compared the results with non-pregnant/lactating (as control group) during the COVID-19 pandemic in Iran.Methods: A cross-sectional study among married women in range of 18 to 45 years via online questionnaires was conducted from 20 March to 25 April, 2020. A total of 604 valid questionnaires were analyzed, including 200 pregnant women, 203 lactating women, and 201 non-pregnant/lactating women. Mental health, COVID-19-related anxiety, and marital satisfaction were respectively assessed by the General Health Questionnaire (GHQ), the Corona Disease Anxiety Scale (CDAS), and ENRICH Marital Satisfaction Scale (EMS Scale). The data were analyzed using Statistical Package for Social Sciences (SPSS) software. Results: The scores of mental health problems in pregnant and lactating women were significantly higher than the control group (18.86±12.56 and 18.83±13.99 vs. 13.01±8.15, P<0.00). The total CDAS score in the control group was significantly less than pregnant women (30.87±10.56 vs. 26.05±6.12, P<0.001) and lactating women (30.80±11.37 vs. 26.05±6.12, P<0.001). The mean of marital satisfaction was significantly lower in the pregnant women (28.06±2.67 vs. 29.64±3.18, P < 0.001) and lactating women (28.74±3.58 vs. 29.64±3.18, p = 0.01) compared with the control group. There was no statistically significant difference in the depression among three groups (P < 0.05).Conclusions: Pregnant and lactating women had more mental health problems, more anxiety and less marital satisfaction in comparison to non-pregnant/lactating women in the course of COVID-19 outbreaks. Further study is needed to investigate the effect of COVID-19 prevalence on mental health and marital satisfaction of pregnant and lactating women, considering the socioeconomic status.