The aim of this study is to investigate the effects of quarantine/social isolation on maternal depression, breastfeeding and sleep quality in mothers who have just given birth during the pandemic period that has affected the whole world. This cross-sectional study included women who gave birth during either in the first peak of the first wave (April, 2020) or the end of the first peak (July, 2020) of the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) pandemic in a tertiary pandemic regional referral centre. A total of 210 patients were enrolled to the study. The research data were collected using specific questionnaires including the Pittsburgh Sleep Quality Index (PSQI), the Edinburgh Postpartum Depression Scale (EPDS) and the Breastfeeding Self-Efficacy Scale-Short Form (BSES-SF). As a result, maternal postpartum depression and sleep quality scores did not differ significantly among postpartum women with different timelines according to the intensity of the SARS-CoV-2 pandemic (p=0.205 and p=0.352, respectively). The Breastfeeding Self-Efficacy Scale was significantly better (p=0.000) in the post-quarantine period than in the early stages of the pandemic when there were strict quarantine regulations. In conclusion, Sleep quality and postpartum depression remained unchanged with regard to the severity of the quarantine among women who gave birth during the SARS-CoV-2 pandemics. The breastfeeding self-efficacy of mothers was found as improved in the post-quarantine period.