Infection with the Alpha and Delta COVID-19 variants was associated with severe infection and worse outcomes for pregnant women.
Women pregnant infected with COVID are more likely to be admitted to an intensive care unit (ICU) or need invasive ventilation. During the pandemic, two separate variants have emerged; alpha and delta, with the former becoming the dominant variant until May 2021, when it was superseded by the latter. While there is evidence that both the alpha and the delta are associated with a greater level of transmissibility and hospitalisations in the non-pregnant population, there is limited published comparative information of the impact of the original (wild-type) and the alpha and delta variants in pregnant women. The evidence that is available, would suggest that the delta variant lead to more admissions to an ICU.
In the absence of such comparative data, a team from the National Perinatal Epidemiology Unit, Nuffield Department of Population Health, Oxford, UK, sought to examine the differences of these different variants on the severity of maternal infection over time. The study was part of the Obstetric Surveillance System which is a research platform that records information on specific pregnancy complications. The primary outcome measure was a composite indicating moderate to severe COVID-19 infection: oxygen saturation < 95% on admission, the need for oxygen therapy, evidence of pneumonia on imaging, admission to an ICU or maternal death. Although the individual patient-level data did not indicate the specific variant responsible for infection, the outcomes were collected for hospitalised pregnant women with confirmed COVID-19 infection or within two days of giving birth, across the periods of time in which the wild-type (original strain), the alpha and delta variant were dominant.
There were 3371 women admitted to hospital across the three time periods and the majority of admissions occurred during the period for which the alpha variant was dominant. From 2521 admissions during this period, just under half (45%) were due to COVID-19. Overall, the proportion of COVID-19 related admissions increased across the variants from 41.1% (wild-type), 45.9% (Alpha) and 54.2% (Delta). The proportion of women hospitalised with at least one marker of moderate to severe disease increased from 25% (wild-type) to 35.8% (Alpha) and 45% (Selta). Women admitted during the alpha period were significantly more likely to require admission to ICU than during the wild-type period (odd ratio, OR = 1.61, 95% CI 1.24–2.10) and while there was a slightly higher rate of admission during the Delta vs Alpha period, this difference was not significant. Fortunately, the majority of babies were live born with no differences in the proportion of stillbirths across the different time periods.
In their discussion, the authors commented on how the delta variant caused the biggest increase in symptomatic pregnant women and appeared to experience more severe disease though the difference was not statistically significant. They concluded that pregnant women appear to be at an increased risk of more severe infection and admission to ICU and should be considered as a priority group for vaccination.
Vousden N et al. Impact of SARS-CoV-2 variant on the severity of maternal infection and perinatal outcomes: Data from the UK Obstetric Surveillance System national cohort. MedRxiv 2021