Lessons for future pandemics: pregnant women admitted to hospital with covid-19 -an IPD meta-analysis of population-based cohorts in ten European countries within the International Obstetric Survey Systems (INOSS)

Objectives: To assess the incidence of covid-19 related hospital admissions in pregnant women, the severity of covid-19 disease and the medical treatment provided to pregnant women with moderate to severe covid-19 disease. Design: Individual Patient Data (IPD) meta-analysis of population-based cohort studies using aligned definitions and case-report forms. Setting: Ten European countries with national or regional surveillance within the International Obstetric Survey Systems (INOSS) collaboration; Belgium, France (regional), Italy, the Netherlands, Denmark, Finland, Iceland, Norway, Sweden(regional) and the United Kingdom. The dominant SARS-CoV-2 variant was the wild type in all countries during the study period. Participants: The source population was 1.7 million women giving birth from 1 March 2020 to 31 December 2020. Exposure: Positive SARS-CoV-2 polymerase chain reaction (PCR) test ≤7 days before hospital admission, during admission or up to 2 days after giving birth, further categorised by admission due to covid-19 or with symptoms (covid-19 admission), or admission for obstetric healthcare or asymptomatic (non-covid admission). Main outcome measures: Incidence of covid-19 admission per 1000 maternities. Moderate to severe covid-19 defined as; maternal death, intensive care admission, or need for respiratory support. SARS-CoV-2 directed medical treatment. Results: Among 1.7 million maternities 9003 women were included, and amongst them 2350 (26.1%) were admitted due to covid-19 or symptomatic. The pooled incidence of covid-19 admission per 1000 maternities was 0.8 ((95%CI 0.5 to 1.2), τ 2 =0.44), ranging from no admissions in Iceland to 1.7 in France and 1.9 the UK. In total, 13 women died. Amongst 2219 women admitted due to covid-19 in countries with complete respiratory support information, 820 women (39.5%, (95%CI 34.6 to 44.4%), τ 2=0.02) had moderate to severe covid-19. At most, 16.8% (95%CI 7.7 to 32.9, I2=81.8, τ 2=0.7) of women with moderate to severe covid-19 received SARS-CoV-2 directed medical treatment with corticosteroids, although 66.6% (95%CI 59.4 to 73.2) I2=50.1, τ 2=0.06) were given thromboprophylaxis. Conclusion: Population-based surveillance in ten European countries from the first ten months of the pandemic showed variation in pregnant womens’ risk of covid-19 admission. This indicates that national public health policies played a substantial and previously unrecognised role in protecting pregnant women. Few pregnant women with moderate to severe covid-19 were given SARS-CoV-2 directed medical treatment, even when there were no or minor safety concerns. Major lessons for future pandemics pertain to the importance of rapid, robust surveillance systems for maternal and perinatal health; and of including use for pregnant women early in the development and testing of medicines and vaccines for public health emergencies. Trial registration; the meta-analysis of the observational national studies was registered in EU PAS (EUPAS40489)