Association Between COVID ‐19 Pandemic Phases and the Risk of Maternal Intensive Care Unit Admission: A Retrospective Analysis of 215,363 Victorian Hospital Admissions
Michele Barrese, Melvin B. Marzan, Lisa Hui ABSTRACT
Background
There are no published Australian population‐based data on serious COVID‐19‐associated maternal morbidity before and after widespread vaccination.
Aims
To compare COVID‐19 infection rates, intensive care unit (ICU) admissions, and length of stay in hospitalised pregnant patients before and after achieving 70% state‐wide maternal COVID‐19 vaccination coverage.
Material and Methods
Population‐based retrospective cohort study involving all hospital‐admitted episodes for pregnant patients over 15‐years‐old with COVID‐19 in Victoria from 1 March 2020 to 31 March 2022. Phase 1 was defined as March 2020—October 2021 when maternal vaccination coverage < 70%; Phase 2 was defined as November 2021–March 2022 when maternal vaccination coverage ≥ 70%. Primary outcomes include COVID‐19 rates, ICU admission rates, and length of stay. A p‐value of < 0.05 was considered statistically significant.
Results
We analysed 215,363 hospital admissions, among which 2,128 (0.99%) had COVID‐19. The percentage of admitted pregnant patients with COVID‐19 was higher in Phase 2 than Phase 1 (3.27% vs. 0.41% respectively, p < 0.001). However, Phase 2 was associated with lower maternal ICU admission rates (2.02% vs. 5.39%, p < 0.001) and lower median length of stay (2.19 vs. 3.11 days, p < 0.001) compared with Phase 1. The risk of COVID‐19 was significantly lower in socioeconomically advantaged pregnant patients (aRR = 0.83 [95% CI, 0.76–0.90], p < 0.001) and pregnant patients ≥ 30‐years‐old (aRR = 0.81 [95% CI, 0.74–0.88], p < 0.001).
Conclusions
Maternal ICU admission risk and length of stay were significantly lower among pregnant patients with COVID‐19 during Phase 2, which is likely due to the combined effects of high maternal COVID‐19 vaccination coverage and changes in SARS‐CoV‐2 variants.