OBJECTIVE: To explore the modifications to maternity services across the UK, in response to the coronavirus disease 2019 (COVID-19) pandemic, in the context of the pandemic guidance issued by the Royal College of Obstetricians and Gynaecologists (RCOG), Royal College of Midwives (RCM) and NHS England. DESIGN: National survey. SETTING: UK maternity services during the COVID-19 pandemic. POPULATION OR SAMPLE: Healthcare professionals working within maternity services. METHODS: A national electronic survey was developed to investigate local modifications to general and specialist maternity care during the COVID-19 pandemic, in the context of the contemporaneous national pandemic guidance. After a pilot phase, the survey was distributed through professional networks by the RCOG and co-authors. The survey results were presented descriptively in tabular and graphic formats, with proportions compared using chi-square tests. MAIN OUTCOME MEASURES: Service modifications made during the pandemic. RESULTS: A total of 81 respondent sites, 42% of the 194 obstetric units in the UK, were included. They reported substantial and heterogeneous maternity service modifications. Seventy percent of units reported a reduction in antenatal appointments and 56% reported a reduction in postnatal appointments; 89% reported using remote consultation methods. A change to screening pathways for gestational diabetes mellitus was reported by 70%, and 59% had temporarily removed the offer of births at home or in a midwife-led unit. A reduction in emergency antenatal presentations was experienced by 86% of units. CONCLUSIONS: This national survey documents the extensive impact of the COVID-19 pandemic on maternity services in the UK. More research is needed to understand the impact on maternity outcomes and experience. TWEETABLE ABSTRACT: A national survey showed that UK maternity services were modified extensively and heterogeneously in response to COVID-19.