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Pregnant women are not at greater risk of severe illness with COVID-19

Results from a large study on the outcomes of 427 pregnant women and their babies during the first wave of the COVID-19 pandemic gave reassurance that pregnant women were at no greater risk of severe illness than other women.

Published: 03 June 2021

A rapid response to the emerging pandemic

NIHR-funded researchers led by Professor Marian Knight, Professor of Maternal and Child Population Health at the Nuffield Department of Population Health at the University of Oxford, have undertaken a rapid study of all pregnant women who were admitted to hospital across the UK with a confirmed infection of COVID-19. 

In their study published in the BMJ, they found that most women had good outcomes that were similar to the general, non-pregnant population. However, it also revealed that more than half of the pregnant women admitted to hospital (56%) were from Black, Asian or other ethnic minority groups. Women with underlying health conditions were also more at risk. Their study contributed to ongoing guidance and policy being developed by the Royal Colleges of Obstetricians and Gynaecologists (RCOG) and Midwives (RCM), NHS England and the Departments of Health of the four UK nations to help them respond to the emerging pandemic. 

Dr Christine Ekechi, Consultant Obstetrician and Gynaecologist, and Co-Chair of The Race Equality Taskforce for the RCOG, said:

 “The findings of the UKOSS study have been fundamental in terms of informing the RCOG development of evidence-based guidance for healthcare professionals supporting women with COVID-19 in pregnancy.”

She continued: “The UKOSS study provided important insights into the impact of COVID-19 on pregnant women and their babies in the UK and has continued to do so throughout.” The study is ongoing and the team will continue collecting and analysing data to inform guidance into 2021.

Identifying the women most at risk

During the 2009–2010 H1N1 swine flu epidemic, pregnant women were at increased risk for developing more serious complications of infection. In preparation for a future flu pandemic, in 2011 the NIHR commissioned a UK-wide study designed to collect information about the characteristics and outcomes of pregnant women and their babies by the UK Obstetric Surveillance System (UKOSS). The study was prepared and put on hold, ready to be activated when needed. The identification and rapid spread of COVID-19 to many countries in early 2020 prompted the activation of the UKOSS team’s pre-planned study.

UKOSS was set up in 2005 by Professor Marian Knight and colleagues at the National Perinatal Epidemiology Unit, University of Oxford, to carry out studies of severe pregnancy complications in the UK. With support from the NIHR Clinical Research Network, doctors and midwives from 194 obstetric units in the UK provided the UKOSS team with details of 427 pregnant women admitted to hospital with confirmed COVID-19 between 1 March 2020 and 14 April 2020. 

The study found that most of the women did not have severe illness and only 41 (10%) needed critical care. Of those, 33 successfully delivered their babies, and the remaining eight women were discharged before giving birth. Overall, a quarter of the 262 women who delivered babies gave birth preterm. Most women with COVID-19 were admitted in the late second or third trimester of pregnancy, supporting guidance for continued social distancing measures in later pregnancy. 

More than half (55%) of pregnant women admitted to hospital with COVID-19 infection were from ethnic minorities. This was a highly disproportionate number given that only 13% of the total UK population identify as ethnic minority and indicated the need for an urgent explanation. Pregnant women with a pre-existing condition, such as diabetes or high blood pressure, and those who were overweight or older were also more likely to be admitted with severe illness. 

The researchers also reported about suspected transmission of COVID-19 from mothers to their babies as it had been unclear if this occurred, and UK guidance was that babies should remain with their mothers after birth. Transmission of COVID-19 from mother to baby was suspected if the baby tested positive in the first 12 hours after birth. This was uncommon though, with six babies testing positive within 12 hours and a further six after 12 hours. Neither vaginal nor caesarean births appeared to be related to a positive test. Five babies sadly died during the study although none of their deaths appeared to be related to COVID-19. 

Professor Andrew Shennan, Professor of Obstetrics at the Department of Women and Children’s Health, King’s College London, said:

“This is by far the largest and most systematic look at pregnancy outcomes in COVID-19 involving 427 women. The outcomes are excellent for the baby, with 97% live births.”

“The chances of serious problems [related to COVID-19] to the mother are very similar to non-pregnant populations. The rare COVID-19 infections did not cause poor outcome to the newborn. Pregnant women can be reassured by this.”

Using the evidence to inform guidance and support research

The UKOSS team’s ongoing analysis of the data has influenced national guidance from the RCOG and the RCM for women and maternity staff on coronavirus infection in pregnancy. Dr Ekechi said: “Crucially, the study also highlighted the ever-deepening health disparities for women from Black, Asian or minority ethnic backgrounds.” 

“This information enabled the RCOG to update its guidance to ensure clinicians were aware of the increased risk for women from these backgrounds and supported the early admission and recognition of illness from COVID-19. Additionally, our advice strongly advocated for women to seek help early where they had concerns, ultimately safeguarding the lives of all pregnant women and their babies, especially those women most at risk."

The NIHR strongly supports studies to share their data to help their research benefit more patients and the wider public. The UKOSS team has shared its evidence and clinical experience widely by contributing their results to the WHO Living Systematic Review of COVID-19 in Pregnancy, led from the University of Birmingham, and to a separate review of studies carried out on COVID-19 in pregnancy by George Washington University. 

The data collected on babies testing positive for COVID-19 were also shared with a separate NIHR-funded UK-wide study of COVID-19 infection in newborn babies, which has helped inform national and international guidance around keeping mother and baby together after birth to a mother with COVID-19. 

Commenting on the collaboration between the studies, Dr Chris Gale, Honorary Consultant Neonatologist and Reader in Neonatal Medicine at Imperial College London, and lead researcher on the COVID-19 infection in newborns study, said: 

“The British Paediatric Surveillance Unit study was greatly strengthened by working closely with UKOSS.”

“It meant that we were able to identify babies born to mothers with COVID very comprehensively through linking with UKOSS and national testing data. Consequently, we were confident that we had identified almost all cases of neonatal SARS-CoV-2 infection where the baby was in hospital. This meant that we were able to report robust, national data demonstrating that neonatal SARS-CoV-2 infection is rare and that short term outcomes for these babies are good. This was internationally unique.”

The study’s results have been widely published by media outlets nationally and internationally, outlining their findings and reiterating the need for pregnant women to maintain social distancing, especially during the third trimester. 

In the wider context of the study being pre-planned and “hibernated” until it was needed, it has shown that the model developed by NIHR and the UKOSS research team was effective, allowing the team to start collecting data from obstetric units within three days of its activation.

Reflecting on the study so far, Professor Knight said: 

“Our study clearly illustrates the benefits of thinking ahead, designing and setting up study infrastructure when threats are only hypothetical.” 

She went on to say: “This is not only because it allowed for rapid collection and analysis of information for pregnant women and their clinicians, but because it allowed for the collection of high quality data and robust study design - thus minimising the risks of publication of, at best, misleading, or, at worst, erroneous, information.”


The study was funded by NIHR’s Health Services & Delivery Research Programme.

More information about the study is available on the NIHR’s Funding & Awards website.

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