After her 13th week of pregnancy, when she went for a routine ultrasound test, the foetus was found to be dead. (Representational)

A first trimester miscarriage in a Mumbai resident is being linked to the SARS-CoV-2 virus after tests found the infection had travelled into the umbilical cord, placenta and possibly caused inflammation in the foetus.

“To our knowledge, this is the first case demonstrating persistence of SARS-CoV-2 infection in a tissue weeks after clearance in the throat swabs… the virus not just survived in the tissue but is replicative in the placental cells,” stated a research paper submitted last week by the National Institute of Research in Reproductive Health (NIRRH) – a research arm of the Indian Council of Medical Research – in collaboration with ESIS (Employees’ State Insurance Scheme) hospital at Kandivali.

The paper was posted on August 22 on MedRxiv, an online site that publishes pre-prints of medical and scientific papers.

The woman, a hospital security guard in her late twenties, tested positive for Covid-19 when she was two months pregnant. She was asymptomatic. Five weeks later, when she was in the 13th week of her pregnancy, her nasal swab test returned negative. But after her 13th week of pregnancy, when she went for a routine ultrasound test, the foetus was found to be dead.

Suspecting it to be linked with Covid-19, ESIS hospital approached the NIRRH to investigate further. The hospital’s ethics committee approved tests on the woman.

“We first tested her nasopharyngeal for Covid-19 again, and it came negative. Then we tested the placenta, amniotic fluid and foetal membrane. We were surprised to find that five weeks after she got the infection, the virus was replicating in the placenta,” said Dr Deepak Modi, placenta biologist in NIRRH.

This was the woman’s third pregnancy. Doctors suspect vertical transmission of virus led to inflammation in the lungs of the foetus, leading to its death.

While vertical transmission, meaning coronavirus travelling in-utero from mother to foetus, has been recorded, instances of miscarriage due to Covid-19 complications are rare.

In Switzerland, a 28-year-old Covid-19 positive woman gave birth to a stillborn baby in second trimester. She was evaluated in Lausanne University Hospital on March 20. The findings published in the Journal of the American Medical Association stated that samples from the umbilical cord and peripheral margin tested positive for Covid-19. The research paper stated that the miscarriage “appears related to placental infection with SARS-CoV-2” and “no other cause of fetal demise was identified”.

Doctors in Mumbai suspect a similar placenta infection leading to the miscarriage. “The placenta acts as a barrier protecting the baby from infections from second and third trimester. But in the first trimester, it is still building as a barrier,” Modi said.

He is studying the placenta during various stages during pregnancy. “We found that there is concentration of ACE-2 enzyme in placenta during the first trimester. It acts as a reservoir for SARS-CoV-2,” he said. ACE-2 acts as an entry point for coronavirus into a human cell and helps it replicate.

The research paper stated that this is the first time the virus was found replicating in the placenta five weeks after infection, and even mounted an inflammatory response in the foetus.

Dr Rahul Gajbhiye, a scientist in NIRRH, said they are maintaining a registry of pregnant women infected with Covid-19 in Maharashtra, but they usually record those due to deliver or have already delivered. Over 1,000 women have been registered.

“Covid-19 infected pregnant women are mostly asymptomatic. We only diagnose them when they come for delivery and get tested. It is possible we are missing miscarriages in first trimester linked with Covid-19 because no tests are being conducted in the first two trimesters,” Gajbhiye said.

The study pointed towards the need for early universal screening of pregnant women to avoid “adverse foetal outcomes”. Globally, there is limited information on impact of Sars-CoV-2 on foetuses.

Dr Prajakta Shende, assistant professor at ESIS hospital’s gynaecology department, said: “The woman had come in contact with an infected patient, so she decided to get tested. When she suffered a miscarriage, we were curious whether Covid-19 had anything to do with it. But so far, we have not begun testing other women in first trimester for Covid-19. “

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