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expert reaction to possible association between COVID-19 and premature birth (re birth of Boris Johnson’s baby)

There have been questions form journalists regarding any possible association between COVID-19 and premature birth. This is in light of the Prime Minister, Boris Johnson’s, son being born.


Prof C.M. (Katia) Bilardo, President of ISUOG (International Society of Ultrasound in Obstetrics and Gynecology), said:

“Some studies with similar viruses have suggested that the baby may not grow as well after an infection similar to COVID-19. Most experts recommend at least one ultrasound 2 to 4 weeks after the end of the infection to make sure the baby is growing well. It is also recommended that regular ultrasound exams continue to be done at least every 4 weeks throughout the pregnancy to check on how the baby continues to grow.

“We call premature birth a birth before 38 weeks, which is when ‘term’ begins. A premature birth may be due to the infection itself or, in some cases, the doctors may decide to induce the delivery earlier if this is better for the mother and the baby.”


Dr Natasha Hezelgrave, Obstetrics and Gynaecology registrar and Preterm Birth Research Fellow, Kings College London, said:

“The global obstetric research community have responded swiftly to this pandemic, observing outcomes from pregnant women with coronavirus, and initiating randomised trials of potential treatments. Reassuringly, pregnant women do not seem to be more likely to contract the virus, nor get more unwell if they do contract the virus compared to other young adults.

“That coronavirus could cause preterm birth is mechanistically possible – we know that many systemic infections and inflammatory states are associated with preterm birth. Whilst there have been some case reports of preterm birth in women infected with coronavirus (some delivered for medical reasons, and some spontaneous) it is not yet clear whether coronavirus is causally related to spontaneous preterm birth.

“Women can be reassured that preterm birth is still rare even with coronavirus infection, with rates observed similar to ‘normal’ background rates. Rarely, infected pregnant women may need preterm delivery if very unwell, to help manage their own health.”


Prof Phillip Bennett FMedSci, Director of Institute for Reproductive and Developmental Biology and Professor of Obstetrics and Gynaecology, Imperial College London and Honorary Consultant in Obstetrics and Gynaecology, Imperial Healthcare NHS Trust at Queen Charlotte’s Hospital, said:

“My understanding is that there is some evidence that COVID-19 is linked to preterm birth, but that it is not clear, at present, whether this is because it causes the onset of preterm labour, or whether women have been delivered to help with the management of their severe respiratory illness. It is the case that seasonal influenza does increase the risk of spontaneous preterm birth, and some evidence that babies born to mothers with ‘flu have worse outcomes (especially PVL brain injury and sepsis in the very early preterm births). But COVID-19 appears to effect pregnant women differently to influenzas, in that ‘flu causes a more severe illness in pregnancy whereas COVID-19 does not seem to do so (our own experience is that it is not a severe illness in pregnancy). More generally URTI are not a cause of preterm birth, except for bacterial pneumonia which is a very strong risk factor. Whether or not a systemic infection is a significant cause of preterm birth may relate to the immunological or inflammatory response that causes it. Bacterial pneumonia is associated with a ‘cytokine storm’ that probably stimulate the onset of labour. My understanding is that severe COVID-19 may do the same and so severe COVID-19 might be a cause of spontaneous preterm labour. Fortunately, at least from my experience, severe disease COVID-19 is rarely seen in pregnant women, but might be an issue in those with underlying comorbidities.

“It is of course also important to bear in mind that preterm birth is common (7-10%), but so probably is COVID-19 infection right now and so the two will often coincide without one being causative of the other. This is also true of other obstetric problems…

“If expected delivery date was early June than Baby Boris would be about 5 weeks early i.e. 35 weeks. This is a late preterm birth, (maybe associated with maternal stress!) which usually have very good outcomes in the UK.”


Dr Sarah Stock, Senior Clinical Lecturer in Maternal and Fetal Medicine, University of Edinburgh, said:

“Preterm birth is birth less than 37 weeks gestation. If Boris and Carrie’s baby was due in early June, then it has been born early. At the moment we don’t know whether COVID-19 infection causes preterm labour or other pregnancy complications that can lead to early birth. Data is needed on infection rates from lots of pregnant women to understand the effects of COVID-19 on women and their babies, and we just do not have that yet.”


Professor Laura Magee, Professor of Women’s Health, King’s College London, said:

“We have just done a systematic review of outcomes among COVID-19-infected women worldwide, and it appears as though iatrogenic preterm birth (in close to 30% of women) and Caesarean delivery (in almost all) were common. However, most of the literature is understandably from China which has a different medical system than ours, and it is not clear if the iatrogenic preterm births were truly necessary. This literature relates to the DIRECT effects of COVID-19 infection in pregnancy. However, there are also potential risks of the change in organisation of maternity care services and the current threshold at which women seek care. Our research will address the direct and indirect effects of the COVID-19 pandemic in pregnancy.”


Statement from the Royal College of Obstetricians and Gynaecologists:

“As this is a very new virus, we are just beginning to learn about it. There is no evidence to suggest an increased risk of miscarriage.

“Emerging evidence suggests that transmission from a woman to her baby during pregnancy or birth (vertical transmission) is probable. There has been a report of two cases in which this seems likely, but reassuringly the babies were both discharged from hospital and are well. In all previously reported cases worldwide, infection was found at least 30 hours after birth. It is important to emphasise that in all reported cases of newborn babies developing coronavirus very soon after birth, the baby was well.

“Given current evidence, it is considered unlikely that if you have the virus it would cause problems with your baby’s development, and none have been observed currently.

“Across the world emerging reports suggest some babies have been born prematurely to women who were very unwell with coronavirus. It is unclear whether coronavirus caused these premature births, or whether it was recommended that the baby was born early for the benefit of the women’s health and to enable her to recover.

“The UK is conducting near-real-time surveillance (observation) of women who are hospitalised and test positive for COVID-19 during pregnancy, through well-established systems already used by all maternity units – this is the UK Obstetric Surveillance System (UKOSS). Imperial College London are also running a surveillance programme (PAN-COVID) to monitor pregnancy and neonatal outcomes for women with COVID-19. We will update our information if and as soon as there is any change in the evidence.

“For further information, please visit the College’s Q&A page on pregnancy and COVID-19.”


Dr Ed Mullins, NIHR Academic Clinical Lecturer, Imperial College London and Obstetrics and Gynaecology registrar, Queen Charlotte’s and Chelsea Hospital, London, said:

“From the reports of women affected by COVID-19 in medical journals up to now, overall around 1 in 20 women are affected by pre-term labour and 1 in 5 women will have pre-term delivery – the reason for delivery is not always clear. Where a reason is given, it may be due to signs of distress in the baby or to allow better treatment for low oxygen levels in the woman. In normal circumstances around 1 in 10 babies would be born pre-term.

“I have no comment on the circumstances of this birth and offer my congratulations to the Prime Minister and Carrie Symonds on the arrival of their baby.”


Prof Christoph Lees, Professor of Obstetrics, Imperial College London, said:

“In the light of the birth of Carrie and Boris’s baby, there is of course speculation as to whether the baby was born preterm and if so whether this could have been linked to the infection by the SARS-CoV-2 virus that his mother had reported symptoms of. While being delighted at his reportedly safe arrival, there is as yet too little data on pregnant women who are infected with the virus but don’t have severe enough symptoms to be admitted to hospital.

“Where a mother is severely ill with COVID-19 requiring hospitalization, this can lead to severe prematurity as the baby will often be delivered for the sake of its own health – and to reduce the burden on the mother’s circulation and lungs in the hope of helping her to recover. If delivery does not occur, in certain circumstances the pregnant woman’s oxygen levels can fall dramatically risking both mother and baby.

“But we don’t know the effect of the SARS-CoV-2 virus on a pregnancy and specifically the risk of miscarriage, premature delivery and fetal growth restriction where an infection is relatively mild and does not need hospitalization. This is a really important question as there are likely to be many hundreds of thousands of women exposed to the virus at all stages of pregnancy in Europe, and millions worldwide. This is the aim of the PAN-COVID UK & International registry, led by Imperial College London in partnership with Cardiff University and funded by the UK’s NIHR, which starts recruiting tomorrow”


Prof Andrew Shennan, Professor of Obstetrics, Kings College London and Director of Tommy’s Preterm Birth Clinic, Guy’s and St Thomas’ Hospital, said:

“There is currently no evidence that coronavirus causes preterm labour. Incidence of early labour is similar to other women. There is very little risk of transmission of virus to the baby. If a mother is incidentally unwell with the virus, she may need early delivery to help manage her health.”


Prof Marian Knight, Professor of Maternal and Child Population Health, University of Oxford, said:

“Acute illnesses which cause fever can be associated with premature labour and birth. However, most premature births in association with COVID-19 in published reports from China and elsewhere have been due to early caesarean births in women with acute illness who are having COVID-related breathing difficulties or whose babies are in distress, rather than because of premature labour. These early births have been reported in women who are acutely ill with COVID-19 rather than women who have had COVID-19 symptoms but then recovered.”


Prof Alexander Heazell, Professor of Obstetrics and Director of the Tommy’s Research Centre, University of Manchester, said:

“This birth would be counted as premature.

“There are mixed data about COVID and preterm birth. A systematic review of SARS-1 and COVID cases thus far suggests the preterm birth rate was roughly double the normal rate.”


Prof Andrew Whitelaw, Emeritus Professor of Neonatal Medicine, University of Bristol, said:

“If the expected date of delivery was said to be early summer, I would interpret that as early June. The definition of preterm is less than 37 weeks gestation. Assuming the baby was born on 29th (or 28th) April, this would be about 5 weeks before EDD i.e. about 35 weeks gestation i.e. preterm. If the EDD was early July, then the gestational age would have to be less than 32 weeks. It would be good to know the birth weight.

“With the scanty information available, Covid-19 does not appear to be a major risk factor for preterm birth. There have been reports from China of newborn infants born to mothers with active Covid-19 but the infants have not had serious illness.”


All our previous output on this subject can be seen at this weblink:


Declared interests

Prof Marian Knight: “I am currently running national surveillance of COVID-19 in pregnancy in the UK.”

Dr Ed Mullins is a co-Principal Investigator of the PAN-COVID project.

Prof Christoph Lees is a co-Principal Investigator of the PAN-COVID project.

None others received.

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