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Research on impacts of severe COVID-19 infection on pregnancy outcomes

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New study shows significant impacts of severe COVID-19 infection on pregnancy outcomes

A new analysis from Oxford Population Health has found that pregnant women that are 30 years old or more, overweight, of mixed ethnicity or have gestational diabetes have a greater risk of contracting severe COVID-19, which poses significant risks for both mother and baby.

Throughout the COVID-19 pandemic, increasing evidence has shown that severe COVID-19 infection in pregnant women significantly raises the risk of adverse outcomes for both mother and baby.

Today, researchers from Oxford Population Health's National Perinatal Epidemiology Unit (NPEU) have published a new analysis of the impacts of COVID-19 infection on pregnancy. In addition, the study identifies several risk factors associated with severe COVID-19 infection in pregnant women, which could help clinicians to identify the most vulnerable women. The results are published in Acta Obstetricia et Gynecologica Scandinavica.

The study used data from the UK Obstetric Surveillance System (UKOSS), which collects information from all 194 UK hospitals with a consultant-led maternity unit. All pregnant women admitted to hospital with confirmed SARS-CoV-2 infection between 1 March 2020 and 31 October 2021 were included in the analysis.

Out of an estimated 1.1 million women who gave birth in the UK during this period, 4436 were admitted to hospital with confirmed SARS-CoV-2 infection. Overall, two thirds (65%) of these women had mild COVID-19 infection; 21% had moderate infection; and 14% had severe infection. In total, 22 of the women died (all with severe COVID-19 infection) during pregnancy, 59 babies were stillborn and ten infants died in the neonatal period.

Women with severe COVID-19 infection were significantly more likely to experience adverse pregnancy outcomes. Compared with women who had mild or moderate infection, women with severe COVID-19 infection:

  • Were more likely to give birth early (before 32 weeks of pregnancy): 22.6% vs 2.7%
  • Had a 50-fold higher risk of their birth being induced or by caesarean specifically due to their COVID-19 infection
  • Were more likely to give birth by pre-labour caesarean section (76% vs 30%)
  • Had a higher proportion of stillborn babies (3.3% vs 1.2%)
  • Had a 12-fold increased risk of their babies being admitted to a neonatal intensive care unit, in part due to the increase in preterm birth.

Several characteristics were independently associated with a greater risk of severe COVID-19 infection. Compared with women who had mild or moderate infection, women with severe COVID-19 infection:

  • Were 48% more likely to be aged 30-39 years, and 2.6-fold more likely to be 40 years or older
  • Were more likely to be of Black, Asian and Other ethnic groups, compared to being of White ethnicity
  • Were more than twice as likely to be obese compared to those with mild to moderate infection
  • Were 43% more likely to have gestational diabetes
  • Were more than twice as likely to have pre-existing hypertension.

Furthermore, over three quarters (77%) of all the women admitted were in their third trimester, indicating that this stage of pregnancy may carry a particularly high risk of hospitalisation from COVID-19.

The analysis also revealed that, for women admitted from 1 July 2020 onwards, only a minority were offered a standard treatment for COVID-19, despite guidance being available at the time. Only 43% of women with severe infection and 26% of women with moderate infection received either an antiviral, Tocilizumab, steroid treatment or monoclonal antibodies.

Nevertheless, COVID-19 vaccination offered significant protection from hospital admission. Of the 1761 women whose vaccination status was recorded, 97% were unvaccinated, 2% had received their first dose, and 1% had received two doses.

The researchers hope the findings will be used to prioritise efforts to tackle vaccine misinformation towards those at highest risk.

Marian Knight, Professor of Maternal and Child Population Health at NPEU, who led the study, said: 'This new analysis shows that certain pregnant women admitted to a hospital with COVID-19 face an elevated risk of severe disease. However, it shows once again the strongly protective effect of vaccination against severe disease and adverse outcomes for both mother and baby. This study emphasises the importance of ensuring that interventions to promote vaccine uptake are particularly focused towards those at highest risk.'

Professor Dame Lesley Regan, Consultant Obstetrician and Chair of Wellbeing of Women, said 'It is understandable that the ongoing COVID-19 pandemic has created fear, worry and uncertainty for women thinking about having a baby and those who are already pregnant. Unfortunately, COVID-19 has also worsened existing health and social inequalities, particularly among pregnant women from ethnic groups.

'We call for urgent action to address these stark inequalities and the gender data gap. The upcoming Women’s Health Strategy offers a real opportunity to tackle these issues and ensure no woman is left behind.'