A major international study has confirmed findings first made by Irish scientists about a link between Covid-19 infection in pregnant women and stillbirth.

The study looked at 68 perinatal deaths in Ireland and 11 other countries and found 65 were caused by inflammation of the placenta linked to Covid-19 infection.

In more than three-quarters of the cases, the placenta was severely damaged and unable to deliver oxygen and nutrients to the growing baby, according to the study published in Archives of Pathology & Laboratory Medicine.

Hospital Report

The babies examined for the study were either stillborn or died within seven days of being born. All the mothers were unvaccinated and had been infected with coronavirus while pregnant.

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One factor behind SARS-CoV-2 placentitis is a build-up of a protein called fibrin, which causes clotting in the placenta, the organ that supplies nutrients and oxygen to the foetus in the womb, according to researchers. The condition also involves the death of protective cells and unusual inflammation in the placenta.

Complications

Damage to a small part of the placenta does not necessarily result in complications for a pregnancy, but in these instances the damage was widespread. In some cases, more than 90 per cent of the placenta was dead.

At the start of the Covid-19 pandemic, there were no indications that pregnant women were at any greater risk from infection than other women, but as new variants spread the virus was linked to adverse outcomes in pregnancy.

In January 2021, doctors in Cork University Hospital (CUH) published the first report of Covid-related placentitis, and in April that year the Royal College of Physicians in Ireland (RCPI) issued a statement about the first cluster of cases reported worldwide.

The RCPI detailed six cases of stillbirth and one miscarriage caused by SARS-CoV-2 in Ireland over the preceding four months. All related to the Alpha variant of the virus.

The statement provoked some scepticism within the medical community. Viruses such as zika or syphilis can attack the foetus, but in this instance it appeared the stillbirths were the result of an attack on the placenta.

The association between Covid-19 infection and stillbirth was confirmed last November by the US Centers for Disease Control and Prevention, which found pregnant women with the virus had an increased risk of stillbirth compared with uninfected women.

Identified

At least 18 Irish cases of Covid-related placentitis resulting in stillbirth have now been identified by pathologists Dr Brendan Fitzgerald in CUH and Dr Noel McEntagart in the Rotunda Hospital. All involved women who were not vaccinated.

“We’ve seen how the stillbirth birth rate increased during the pandemic with the Alpha and Delta waves of the virus,” said Prof Keelin O’Donoghue, consultant obstetrician at CUH. “We don’t know yet about the possible impact of Omicron.”

About 1 per cent of unvaccinated pregnant women with Covid are at risk of placentitis, which can lead to stillbirth. “This is a very good reason for expecting mothers to get vaccinated,” said Prof O’Donoghue.

After the CUH doctors identified the cluster of Covid-related placentitis, vaccination for pregnant women was prioritised. Monitoring has also been increased for pregnant women with Covid-19, particularly those who are not vaccinated.