Research shows mothers may pass coronavirus to babies during pregnancy, but risk is low

New research this week has reported 2 cases of Covid-19 being passed from mothers to their babies in the womb. Doctors have reassured pregnant women that, although this can happen, the risk is very low and these families are now fully recovered.

July 14 2020

While the pandemic is so new, the long-term effects of catching Covid-19 during pregnancy are not yet clear, but evidence so far had suggested the placenta would act like a barrier to stop the virus crossing over from mother to baby. In the few previous cases when babies had been diagnosed, it wasn't possible to tell if it was transmitted during or soon after birth. 

This week, research journals have published case studies of babies born with Covid-19 who doctors can say definitely contracted the virus in the womb: Nature Communications reports that a baby boy in France developed the infection prior to birth, and so did a premature baby girl in Texas according to the Paediatric Infectious Disease Journal.

Risk of Covid-19 transmission in pregnancy is low

It’s concerning to learn that babies can be infected with Covid-19 in the womb, but research experts have emphasised that just because this is possible does not mean it’s common; the risk is very low. It’s also important to note that both affected families have made a good recovery.

Daniele De Luca, medical director of paediatrics and neonatal critical care at the Antoine Béclère hospital in Paris where the baby boy was born with Covid-19, explained: “Pregnant women should be reassured - pregnancy is very controlled and if you have something like this, it can be controlled. In most cases, there will be no damage to the baby. There are many things we can do, but clinicians must be aware that this may happen.”

The rarity of these cases was further emphasised by Dr Julide Sisman from the University of Texas Southwestern Medical Centre in Dallas, where the baby girl was born with the virus, who said: “Intrauterine transmission of Covid-19 appears to be a rare event.”

Another researcher on the Texas team, Dr Amanda Evans, added: “Numerous infants have now been delivered to pregnant women diagnosed with Covid-19, with the majority of these infants without respiratory illness or positive molecular evidence for Covid-19.”

Our research shows most pregnant women don't pass on the virus 

Andrew Shennan, who runs Tommy’s Premature Birth Clinic and is professor of obstetrics at King’s College London, also says it’s rare for mothers to pass Covid-19 on to their babies.

“In 244 live born babies of infected mothers in the UK, 95% had no sign of the virus, and outcomes are similar to non-infected babies. Women can remain reassured that pregnancy is not a significant risk factor for them or their babies with Covid-19.”

Prof Shennan is among many Tommy’s researchers working to better understand how the virus affects pregnant women and their babies. Research can't be published before strict review processes, so the evidence currently available is limited - but the work is happening, and we will continue to share important developments when we can.

Follow government pandemic guidance to minimise risk

We understand that you may be feeling worried about pregnancy and Covid-19, so Tommy’s has lots of of Covid-19 information and advice specifically for expectant and new parents. We would advise you follow these guidelines, which are being updated as new information is published.

Dr De Luca said that social distancing and hand washing to reduce the risk of infection “is important whether you are pregnant or not.” 

Our midwifery manager Kate Marsh advised: “All pregnant women should follow the government’s advice. If you think you may have symptoms of coronavirus, you should use the NHS 111 online service for information, or NHS 24 if in Scotland. You should also contact your maternity unit to inform them that you have symptoms suggestive of coronavirus, particularly if you have any routine appointments in the next 7 days.

“The team are there to support you and the important thing is to speak to your midwife or doctor if you're worried about your pregnancy. If you are from a Black, Asian and minority ethnic (BAME) background, your maternity team may also book you additional appointments, or refer you to a doctor or specialist clinic if there are concerns about your health or your baby’s health.”

Ongoing studies of coronavirus in pregnancy

Scientists from our teams across the UK are collecting placental tissue from mothers with Covid-19 for analysis. The team at Tommy’s Manchester Stillbirth Research Centre is using electron microscopy to closely examine cells from the placenta to see if the virus is present; Dr Carolyn Jones, who retired some years ago, has come back to do this as she is one of the leading experts in this technique.

These placenta cells, as well as blood samples, will be stored in our National Reproductive Health Biobank to be used in research studies. Our biobank collects samples from pregnant and non-pregnant women and their babies, including those who have tested positive with Covid-19. The samples donated by patients are linked to medical history and pregnancy outcome, as well as to the baby’s health, using the latest technology.

We're also carrying out a number of Covid-19 specific research studies to better understand the potential impact of coronavirus on pregnancy and birth, and how to provide appropriate treatment and support for women and their babies.

“Tommy’s exists to make pregnancy and birth safer for everyone - but we still have so much to learn, particularly in relation to Covid-19. Our National Reproductive Health Biobank will enable us to find out more in real time.” Jane Brewin, Tommy's chief executive