Newborns From Infected Mothers Have SARS-CoV-2 Antibodies

Maternal immunoglobulin G (IgG) antibodies to SARS-CoV-2 infection may be transferred across the placenta from infected pregnant women to their birthed children, according to new research.

In layman’s terms, investigators from the Children’s Hospital of Philadelphia (CHOP) have observed neonatal protection from coronavirus 2019 (COVID-19) in newborns whose mothers were infected with the virus, regardless of their symptom status.

The findings from a 1700-plus patient cohort assessment, published in JAMA Pediatrics, are among the first to observe transplacental transfer of maternal SARS-CoV-2 specific antibodies to newborns from expecting women with either symptomatic or asymptomatic COVID-19.

Led by Dustin D. Flannery, DO, MSCE, of the CHOP Division of Neonatology, investigators sought to understand the dynamics of maternal antibody response to SARS-CoV-2 infection during pregnancy and how—if at all—antibodies may transfer to newborns to provide early protection to the pandemic virus.

As Flannery and colleagues noted, such observations may also influence currently needed strategies for COVID-19 vaccination during pregnancy.

“Newborn protection from infection is primarily dependent on neonatal innate immune responses and maternally derived, transplacentally acquired antibodies,” investugators wrote. “The extent to which maternal antibodies produced in response to SARS-CoV-2 infection during pregnancy cross the placenta is important for understanding potential neonatal protection from COVID-19 and for developing appropriate maternal vaccination strategies when effective vaccines are widely available.”

Investigators conducted their cohort study via data of 1714 women to deliver birth at Pennsylvania Hospital from April 9 – August 8, 2020. Antibody measures were observed in 1471 mother/newborn dyads through maternal and cord blood sera.

Median pregnant patient age was 32 (IQR, 28-35) years old, with 51.3% reported as White/non-Hispanic, 26.3% as Black/non-Hispanic, 11.8% as Hispanic, and 7.3% as Asian. Among the 1471 dyads with available matched sera, investigators observed SARS-CoV-2 IgG and/or immunoglobulin M (IgM) antibodies in 83 (6%) women at delivery.

Among the 83 newborns from mothers with SARS-CoV-2 antibodies, 72 (87%) had observable IgG antibodies in their cord blood. Investigators did not observe any IgG antibodies in cord blood, and antibodies were not detected in any infant born to a mother seronegative for SARS-CoV-2 infection.

Among the 11 seronegative infants born to seropositive mothers, 5 (45%) were born to mothers with IgM antibodies only, and 6 (55%) were born to mothers with significantly lower IgG concentrations than those also positive for SARS-CoV-2.

Investigators observed a placental transfer ratio of >1.0 among women with asymptomatic SARS-CoV-2 infections, as well as those with mild, moderate, and severe COVID-19. Transfer ratio increased with greater time between maternal infection onset and newborn delivery.

Flannery and colleagues concluded a series of observations from the cohort:

• Placental and neonatal SARS-CoV-2 transmission is, at best, uncommon.
• The greater risk of newborn infection is postnatally, from contagious mothers or other household contacts.
• Maternal antibody concentrations and transfer ratio were positively correlated with increasing time between maternal infection and time of delivery.
• Optimal maternal vaccination for COVID-19 during pregnancy will need to consider maternal and fetal factors to ensure neonatal protection.

“Our findings demonstrate the potential for maternally derived antibodies to provide neonatal protection from SARS-CoV-2 infection and will help inform both neonatal management guidance and design of vaccine trials during pregnancy,” they wrote. Further studies are needed to determine if SARS-CoV-2 antibodies are protective against newborn infection.”