What are the risks of Covid-19 in pregnancy?

15 November 2021

We have been asked lots of questions on WhatsApp about the risks of Covid-19 in pregnancy. The evidence so far shows that you are not more likely to be infected with Covid-19 during pregnancy, but pregnant women who do catch it are more likely to be admitted to intensive care. There are also higher rates of complications to pregnancy and delivery when women require hospital treatment for Covid-19. We spoke to experts to find out more. 

Are pregnant women more likely to get Covid-19?

The Royal College of Obstetricians and Gynaecologists (RCOG) says that based on the evidence to date, pregnant women do not appear to be any more likely to get Covid-19 than other adults.

However, pregnant women are at a slightly increased risk of becoming severely unwell if they do catch Covid-19, particularly later on in pregnancy. If this happens there is also an increased risk of complications to the pregnancy, such as the baby being delivered early.

There is also evidence of an increased risk of pre-eclampsia and caesarean section, and emerging evidence around an increased risk of stillbirth, although this finding hasn’t always been consistent.    

Covid-19 in pregnancy has been a point of particular interest and concern because pregnant women undergo a number of immunological and physiological changes that could alter the way that they respond to Covid-19. 

Marian Knight is professor of maternal and population health at the University of Oxford and programme lead of MBRRACE-UK, which monitors and investigates the causes of maternal deaths, stillbirths and infant deaths in the UK. She told Full Fact that the immune system changes during pregnancy, because the body has to tolerate the presence of a foetus and placenta which are “immunologically different” from the mother—this can mean pregnant women are less able to “respond and fight off certain infections”. 

Professor Knight also explained that part of the reason pregnant women can be more severely affected in later pregnancy is because the “baby bump” can affect lung capacity and ability to breathe if you develop a lung infection, as can occur with severe Covid-19. 

Are pregnant women likely to have more severe illness with Covid-19?

Using data from a number of sources, the RCOG has said that approximately two-thirds of pregnant women with Covid-19 have no symptoms at all, and many pregnant women who do have symptoms only have mild or flu-like illness. 

Statistics on this vary, depending on which point during the pandemic data was taken. For example, early in the pandemic, testing in the UK was only conducted on people who had symptoms. Estimates from this time period will therefore show a higher proportion of symptomatic cases. 

Health bodies have used an array of studies from the UK and from abroad, as well as observational findings and case studies, to try to characterise the risk of Covid-19 in pregnancy. There are difficulties in giving absolute numbers around this because of differences in the populations and healthcare provisions across different countries, changing dynamics of the pandemic, and because of an awareness that clinicians may be likely to take a more cautious approach regarding steps like admission to hospital or to an intensive care unit when a woman is pregnant.

Some pregnant women are more at risk of being unwell with Covid-19 than others—for example those from a black and minority ethnic background, and those with underlying health problems. 

Studies have shown that pregnant women with Covid-19 have been more likely to be admitted to an intensive care unit than non-pregnant women with Covid-19, particularly later in the pandemic.

Data from the Intensive Care National Audit and Research Center (ICNARC) shows that between September 2020 and April 2021, 2,289 women aged 16 to 49 with Covid-19 in England, Wales and Northern Ireland were admitted to critical care, and 319 (14%) were recently or currently pregnant. Between 1 May 2021 and 5 November 2021 1,606 women of child bearing age with Covid-19 were admitted to critical care age and of these, 463 (29%) were pregnant or had recently been pregnant. 

These figures suggest a disproportionate number of pregnant women with Covid-19 end up in critical care. It is estimated 7.5% of women aged between 15 and 44 in the UK are pregnant at any one time. In previous ICNARC reports (using data from 2009-2012, pre Covid-19), pregnant women have made up approximately 12% of female intensive care admissions aged 16 to 50. 

Summarising the findings of a number of studies and data reports, the RCOG says pregnant women with Covid-19 are at a slightly increased risk of severe Covid-19, particularly during later pregnancy. 

Professor Knight told Full Fact: “In the first wave of the pandemic, the information was relatively reassuring and it didn't look as if ...pregnant women were substantially more likely to have severe outcomes compared with women who were not pregnant. 

“But with the Alpha variant, outcomes became worse for pregnant women. And then with the Delta variant, it's worse again. There's absolutely no doubt in my mind now that pregnant women are more likely to have severe outcomes than non-pregnant women”.

She added that pregnant women with Covid-19 who are asymptomatic do not appear to have any worse outcomes than any other pregnant woman. However, among pregnant women who are admitted to hospital with symptoms of Covid, “45% of women will need a caesarean birth”, “10% will need intensive care”, and “less than 0.5% will die”. Professor Knight also said that figures for recent months rather than the pandemic as a whole “appear slightly worse”, with the emergence of variants such as Delta and Alpha.

The RCOG has also highlighted NHS figures which show that between July and October 2021, one in five of the adults with Covid-19 admitted for Extra Corporeal Membrane Oxygenation (ECMO) were pregnant women. ECMO acts as a lung bypass machine and is one of the highest levels of respiratory support available.

Up until September 2021, 33 pregnant women (or women who were pregnant within the past six weeks) have died of Covid-19 in the UK.The stats above apply to all pregnant women, whether vaccinated or unvaccinated. However, Dr Edward Morris, President of the RCOG, said: “More than 98% of the pregnant women admitted to hospital with symptoms of COVID-19 were unvaccinated, which provides strong evidence on the effectiveness of the vaccine in preventing serious illness.”

What about complications to pregnancy?

The RCOG has said that for pregnant women who are very unwell with Covid-19 (for example, those who are admitted to hospital with the infection), it is two to three times as likely that their baby will be born early. This is shown in data from studies such as The PregCOV-19 Living Systematic Review (which included lots of earlier trial results). These studies also show that the babies were usually delivered early due to medical advice on the basis of health needs for the mother, and sometimes needs of the foetus.  

The UK Obstetric Surveillance Study (UKOSS) report published in May 2021 included data from 1,148 pregnant women with Covid-19 who were admitted to hospital between March and September 2020. Nearly one in five women with symptomatic Covid-19 gave birth prematurely. However, women who tested positive for Covid-19 but had no symptoms were not more likely to give birth prematurely. 

Studies have also shown that the babies of women with Covid-19 also appear to be more likely to be admitted to the neonatal unit, and be born by cesarean section. 

Professor Knight added that being born preterm “can have lifelong consequences for learning and development” and it is a “really big and important impact that we need to be thinking about when thinking about the risks of Covid for pregnant women”.

Two important studies have shown conflicting results regarding the risk of stillbirth or infant death. The UKOSS study of 1,148 pregnant women with Covid admitted to hospital showed   no statistically significant increase in stillbirth rate or infant death for babies born to women who had Covid-19. However another recent study has suggested that pregnant women who tested positive for Covid-19 at the time of birth were twice as likely to have a stillbirth, although the actual number of stillbirths remains low (8.5 per 1,000 in women who had Covid-19 at birth, compared with 3.4 per 1,000 in women who did not have Covid-19 at birth). This study design has been criticised though, as potentially introducing bias and therefore overestimating the risk. The NHS states that there is “emerging evidence that the risk may be higher if you have Covid-19 at the time of birth”. 

The RCOG has said that there is no evidence that Covid-19 increases the risk of miscarriage in early pregnancy. 

What effect does Covid-19 infection have on the baby? 

The UKOSS report from January 2021 included over 1,000 pregnant women who had Covid-19 and were admitted to hospital between March and September 2020.  Only a smaller sample of the babies were tested, but of those that were, approximately 2% tested positive for Covid-19. 

Professor Knight said: “In terms of babies getting [Covid-19] infection, numbers are very, very tiny. So it's quite reassuring in terms of baby infections.” 

The RCOG has said that there have been no reports of Covid-19 infection itself interfering with the development of a baby.

It also said that in most of the reported cases of newborn babies developing Covid very soon after birth, the babies remained well.

The information included in this article contains the latest evidence and official guidance available at the time it was written. This is not a substitute for medical advice. If you require specific medical advice please consult your GP or midwife.

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