Background: People using maternity services in the United Kingdom (UK) have faced significant changes brought on by the COVID-19 pandemic and social distancing regulations. We focused on the experiences of pregnant women using UK maternity services during the pandemic and the impact of social distancing rules on their mental health and wellbeing. // Methods: We conducted 23 qualitative semi-structured interviews from June 2020 to August 2021, with women from across the UK who experienced a pregnancy during the pandemic. Nineteen participants in the study carried their pregnancy to term and four had experienced a miscarriage during the pandemic. Interviews took place remotely over video or telephone call, discussing topics such as mental health during pregnancy and use of UK maternity services. We used reflexive thematic analysis to analyse interview transcripts. // Results: We generated six higher order themes: [1] Some pregnancy discomforts alleviated by social distancing measures, [2] The importance of relationships that support coping and adjustment, [3] Missed pregnancy and parenthood experiences, [4] The mental health consequences of birth partner and visitor restrictions, [5] Maternity services under pressure, and [6] Lack of connection with staff. Many participants felt a sense of loss over a pregnancy experience that differed so remarkably to what they had expected because of the pandemic. Supportive relationships were important to help cope with pregnancy and pandemic-related changes; but feelings of isolation were compounded for some participants because opportunities to build social connections through face-to-face parent groups were unavailable. Participants also described feeling alone due to restrictions on their partners being present when accessing UK maternity services. // Conclusions: Our findings highlight some of the changes that may have affected pregnant women’s mental health during the COVID-19 pandemic. Reduced social support and being unable to have a partner or support person present during maternity service use were the greatest concerns reported by participants in this study. Absence of birth partners removed a protective buffer in times of uncertainty and distress. This suggests that the availability of a birth partner or support person must be prioritised wherever possible in times of pandemics to protect the mental health of people experiencing pregnancy and miscarriage.