Abstract Objective: To describe the clinical characteristics and outcomes of pregnant women with coronavirus disease (COVID‑19) on a national scale in Japan. Design: A nationwide questionnaire-based survey forwarded to all 2185 maternity services in Japan. Setting: A total of 1418 obstetric units that responded (65% of all delivery institutions in Japan). Population: Pregnant women with COVID-19 diagnosed between January and June 2020. Methods: Data were extracted from the questionnaire results. Main outcome measures: Incidence of pregnant women with COVID-19 and infant infection, positive rate of the universal screening test for asymptomatic pregnant women, identification of infection route, and rates of maternal death, severe cases, and caesarean sections. Results: Seventy-two pregnant women were reported to be diagnosed with COVID-19. The positive rate of the universal screening test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) for asymptomatic pregnant women was 0.03% (2/7428). The most common route of infection was familial (57%). Fifty-eight pregnant women with COVID-19 were symptomatic; of whom five (8.6%) had a severe infection and one patient died (a tourist). Severe respiratory symptoms, oxygen administration, and pneumonia were frequently reported in the third trimester and postpartum period compared to early pregnancy (22.2% vs. 2.5% [p=0.03], 38.9% vs. 7.5% [p=0.01], and 50.0% vs. 7.5% [p<0.01], respectively). All pregnant women with COVID-19 underwent caesarean section, regardless of symptoms. There was no SARS-CoV-2 transmission to the newborns. Conclusion: The importance of infection prevention should be emphasized, especially in pregnant women, their families, and their roommates during late pregnancy.

Objective: To identify the characteristics of and measures taken by Japanese medical facilities providing maternity services that have recorded cases of nosocomial infection with SARS-CoV-2, which causes coronavirus disease 2019 (COVID-19). Design: A nationwide questionnaire survey: case-control study. Setting: Medical facilities providing maternity service in Japan. Population: 1,418 medical facilities providing maternity service (65% of all delivery facilities in Japan). Methods: A nationwide questionnaire survey about nosocomial COVID-19 was conducted in July 2020. A case-control study was conducted by including medical facilities providing maternity service with (Cases) and without (Control) nosocomial COVID-19. Main outcome measures: Contributed characteristics and variables associated with nosocomial COVID-19. The number of treated pregnant women with COVID-19 until June 2020 and cases of nosocomial COVID-19 in Japan. Results: Seventy-five COVID-19-positive pregnant women were treated in 48 facilities. Responses from Nosocomial infection was reported in 4.1% of the facilities. Nine reports developed a nosocomial infection in the maternity ward or obstetric department. Variables that contributed to nosocomial COVID-19 were chest CT on admission (adjusted odds ratio [95% confidence interval], 4.76 [2.44–9.27]), PCR test for SARS-CoV-2 before delivery (2.27 [1.21–4.25]), transfer of pregnant women with fever to another hospital (0.21 [0.06–0.71]), and private clinics (0.17 [0.05–0.60]). Conclusion: Nosocomial infection is likely to occur in large hospitals that treat a higher number of patients than private clinics do. Nosocomial infection can occur even in medical facilities performing COVID-19 screening tests, such as chest CT and PCR test.