Pregnant women admitted to hospital with covid-19 in 10 European countries: individual patient data meta-analysis of population based cohorts in International Obstetric Survey Systems

Abstract

Objectives: To assess the incidence of hospital admissions for covid-19 disease in pregnant women, severity of covid-19 disease, and medical treatment provided to pregnant women with moderate to severe covid-19 during the first 10 months of the pandemic.

Design: Individual patient data meta-analysis of population based cohorts in International Obstetric Survey Systems.

Setting: 10 European countries with national or regional surveillance within the International Obstetric Survey Systems (INOSS) collaboration using aligned definitions and case report forms: Belgium, France (regional), Italy, the Netherlands, Denmark, Finland, Iceland, Norway, Sweden (regional), and the UK. The dominant variant of the SARS-CoV-2 virus was the wild-type variant in all countries during the study period (1 March 2020 to 31 December 2020).

Participants: The source population was 1.7 million women giving birth (maternities) from 1 March 2020 to 31 December 2020; pregnant women were included if they were admitted to hospital and had a positive polymerase chain reaction test for the SARS-CoV-2 virus ≤7 days before hospital admission, during admission, or up to two days after giving birth. We further categorised the hospital admission in two groups; covid-19 admission (hospital admission due to covid-19 or with reported symptoms of covid-19 disease) or non-covid-19 admission (admission to hospital for obstetric healthcare or no symptoms of covid-19 disease).

Main outcome measures: Incidence of hospital admissions for covid-19 per 1000 maternities, frequency of moderate to severe covid-19 disease, and number of women who received specific medical treatment for SARS-CoV-2 infection. Moderate to severe covid-19 disease was defined as maternal death, admission to an intensive care unit, or need for respiratory support.

Results: Among 1.7 million maternities, 9003 women were included in the study: 2350 (26.1%) were admitted to hospital because of covid-19 disease or had symptoms of disease. The pooled incidence of hospital admissions for covid-19 per 1000 maternities was 0.8 (95% confidence interval (CI) 0.5 to 1.2, τ²=0.44), ranging from no hospital admissions in Iceland to 1.7 in France and 1.9 in the UK. 13 women died due to covid-19. Among 2219 women admitted to hospital for covid-19 in countries with complete information on respiratory support, 820 women (39.5%, 95% CI 34.6% to 44.4%, τ²=0.02) had moderate to severe covid-19 disease. At most, 16.8% (95% CI 7.7% to 32.9%, I²=81.8%, τ²=0.7) of women with moderate to severe covid-19 received specific medical treatment for SARS-CoV-2 infection with corticosteroids, although 66.6% (59.4% to 73.2%, I²=50.1, τ²=0.06) were given thromboprophylaxis.

Conclusions: Population based surveillance in 10 European countries during the first 10 months of the covid-19 pandemic showed variations in the risk of hospital admissions for covid-19 in pregnant women. This finding indicates that national public health policies likely had a substantial and previously unrecognised role in protecting pregnant women. Few pregnant women with moderate to severe covid-19 were given specific medical treatment for SARS-CoV-2 disease, even when there were no or minor safety concerns. Lessons for future pandemics include 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.

Keywords: COVID-19; Pregnancy complications; Public health.

Figure 1. Flowchart for the source population, inclusion criteria, hospital admission group (covid-19 disease or symptoms of covid-19 disease), and severity of covid-19, from 1 March to 31 December 2020, in 10 European countries. PCR=polymerase chain reaction test result. Maternities refers to the number of women giving birth.

Figure 2. Incidence of hospital admissions for covid-19 disease per 1000 maternities by country, from 1 March to 31 December 2020. Maternities refers to the number of women giving birth. CI=confidence interval

Figure 3. Pregnant women admitted to hospital for covid-19 disease, or symptoms of covid-19 disease if cause of admission was not known, per 1000 maternities, by month of a positive test result for the SARS-CoV-2 virus based on the polymerase chain reaction (PCR) test and by country, from 1 March to 31 December 2020. Data were not available for December 2020 in France. Because of low numbers in individual countries, results from Denmark, Finland, Iceland, and Norway were combined. Maternities refers to the number of women giving birth

Figure 4. Incidence of moderate to severe covid-19 disease in pregnant women in the covid-19 admission group, by country, from 1 March to 31 December 2020. Moderate to severe covid-19 was defined as maternal death, admission to the intensive care unit, or maximum respiratory support with oxygen by nasal cannula or mask, high flow nasal oxygen or continuous positive airway pressure, mechanical ventilation, or extracorporeal membrane oxygenation. CI=confidence interval

Figure 5. Crude risk ratio for moderate to severe covid-19 disease in pregnant women admitted to hospital for covid-19, stratified by age, obesity, and migrant or ethnic minority background, from 1 March to 31 December 2020, for each country. Non-European migrant background was defined as the mother's country of birth outside of Europe in all countries except the UK. In the UK, minority ethnic background was defined as Black, Asian, mixed, or other ethnic backgrounds. Random effects maximum likelihood model (REML) was used with Hartung-Knapp-Sidik-Jonkman (HKSJ) variance estimator. CI=confidence interval

Figure 6. Proportion of pregnant women with moderate to severe covid-19 who were treated with antiviral medicines, corticosteroids for maternal indication, or thromboprophylaxis. Information about corticosteroids for maternal indication was not available from Italy, and information about thromboprophylaxis was not available from the Netherlands. CI=confidence interval