TORONTO -- Researchers have found that the transmissibility of the virus that causes COVID-19 from mother to newborn is rare, but newborns born to socially vulnerable mothers were more likely to test positive.
The study, on Friday, involved researchers from Beth Israel Deaconess Medical Center, Brigham and Women's Hospital, Boston Children's Hospital and Massachusetts General Hospital.
Researchers looked at a cohort of 255 babies born between March and July 2020 from 11 hospitals in Massachusetts to mothers who had tested positive for COVID-19 two weeks before and 72 hours before delivery.
Out of the 255 newborns, 225 were tested for SARS-CoV-2 of which only six tested positive for the SARS-CoV2, the virus that causes COVID-19. This results in a test positivity rate of 2.7 per cent.
"We believe ours is the first study to dive into the risk factors for mother-to-newborn SARS-CoV-2 transmission. We expected the mode of delivery and/or the degree of maternal illness to increase the risk of newborn infection, but were surprised to find that this was not the case," said lead author Asimenia Angelidou .
While the risk of transmission of SARS-CoV-2 remains rare, researchers say there are other serious health risks for babies born to mothers with COVID-19. Out of the 23 newborns who had to be delivered due to worsening illness from the mother, 17 or 73.9 per cent were delivered prematurely. Babies delivered preterm are at a higher risk of chronic health problems, respiratory complications and developmental disabilities.
The researchers also looked at the "social vulnerability" of the expectant mothers, based on their zip code. Social vulnerability was calculated based on socioeconomic status, fluency in English, race, housing and transportation types and age composition of households.
Mothers who live in neighbourhoods with higher social vulnerability were found to have a 4.95 times higher risk of having their baby test positive for the virus, with a 95 per cent confidence interval after adjusting for maternal symptoms and delivery mode.
"We speculate that living in a socially disadvantaged neighbourhood may be a factor in stress-mediated alterations in the maternal and/or fetal immune response, facilitating SARS-CoV-2 transmission," the study states.​
