Clinical characteristics of pregnant women with COVID-19 in Japan: a nationwide questionnaire survey

BACKGROUND: Few reports have presented an overall view of pregnant women with coronavirus disease 2019 (COVID-19) across an entire country and throughout the entire gestation period. Furthermore, no such reports are available for Japan. We examined the clinical characteristics and outcomes of pregnant women with COVID‑19 on a national scale in Japan. METHODS: A nationwide questionnaire-based survey for all 2,185 maternity services in Japan was conducted between July and August 2020. Information regarding maternal characteristics and epidemiological, clinical, treatment, and perinatal outcomes of pregnant women diagnosed with COVID-19 between 16 January and 30 June 2020 were collected. Main outcome measures were 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, and severe cases. RESULTS: Responses from 1,418 institutions were assessed (65% of all delivery institutions in Japan). Seventy-two pregnant women were reported to have been diagnosed with COVID-19. The positive rate of the universal screening test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among 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 died (a tourist). Severe respiratory symptoms, oxygen administration, and pneumonia were frequently reported in the third trimester and postpartum period compared with in 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 < 0.001], respectively). All pregnant women with COVID-19 underwent caesarean sections, regardless of symptoms. There were no SARS-CoV-2 transmissions to newborns. CONCLUSIONS: In Japan, the number of cases of COVID-19 infection in pregnant women is very low. Compared with early pregnancy, late pregnancy may be a risk factor for exacerbation of symptoms and familial transmission is the most common route of infection. The importance of infection prevention should be emphasised, especially in women in late pregnancy, their families, and any cohabitants.