Study sheds light on immunity transfer from Covid-19 positive mothers to babies

Scientists have assessed pregnant patients admitted for Covid-19 and found antibodies against the novel coronavirus in umbilical cord blood, suggesting the possibility of transferred immunity from mothers to babies.

The study, published in The Annals -- the official medical journal of the Academy of Medicine, Singapore -- periodically analysed samples from 16 pregnant patients admitted for Covid-19 to four tertiary hospitals in Singapore.

According to the research, there was no evidence of mother-to-child transmission of the coronavirus via breast milk or placenta.

In the study, the scientists performed SARS-CoV-2 RT-PCR tests on maternal blood and vaginal swabs, amniotic fluid and umbilical cord blood (UCB), and swabs of the placental and umbilical cord surfaces.

The researchers, including those from the Singapore General Hospital, noted that majority of the infected pregnant women had only mild disease and only two of them, who had risk factors like obesity and older age, had severe infection.

None of the women died, the study noted.

Five pregnancies produced term live-births and two participants had spontaneous miscarriages at 11 and 23 weeks of pregnancy.

The scientists said one patient remained positive for the SARS-CoV-2 infection up to 80 days after initial symptoms but they added that such prolonged shedding of the virus may not indicate actual infectivity.

"Recent reports have highlighted the unpredictable clinical course of Covid-19 infection in pregnancy. Severe maternal disease can manifest prenatally or postnatally and trigger abrupt postnatal decompensation, and its presentation may be delayed up to 14 days from symptom onset," they wrote in the study.

However, based on the systematic screening of samples, the scientists said there was no evidence of maternal-child transmission of the virus.

The researchers also found SARS-CoV-2-specific antibodies in the paired maternal and umbilical cord blood.

But they said this finding may not be conclusive evidence of the transfer of antibodies from mothers to babies since the protective proteins may also be trafficked in cases where the maternal-fetal interface is breached by inflammation.