In a recent Pediatrics journal study, researchers assessed the outcomes of children born to mothers infected during pregnancy with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
In utero, transmission of SARS-CoV-2 from mother to child is possible; however, the mechanisms remain unknown. Previous studies have reported transplacental passage of anti-SARS-CoV-2 antibodies, thus providing some passive protection for neonates. However, the efficiency of placental transfer of antibodies regarding gestational age (GA) at infection and durability of protection remain unknown.
Study: Infants born following SARS-CoV-2 infection during pregnancy. Image Credit: Natalia Deriabina/Shutterstock.com
About the study
The present study assesses neonatal outcomes after SARS-CoV-2 infection during pregnancy. Newborns were included if they were born to mothers infected with SARS-CoV-2 during pregnancy and delivered between April 2020 and April 2021.
Premature neonates and neonates of peripartum SARS-CoV-2 infected persons or mothers without SARS-CoV-2 antibodies were excluded. Demographics, comorbidities, disease severity, and trimester of infection were collected for all mothers. In addition, data on head circumference, GA, height, birth weight, clinical signs at birth, and hearing screening test results were collected for newborns.
All newborns were tested for SARS-CoV-2 within 24 hours of life. Blood samples were taken for total/differential blood cell count, liver function tests, and platelet and hemoglobin levels within 48 hours. Cerebral and abdominal ultrasound and fundus evaluation were performed during the first three months of life.
In a follow-up program, all term infants were assessed at one, three, six, nine and 12 months of age. Serum antibodies against SARS-CoV-2 were determined in mothers and neonates within 48 hours of delivery. Transplacental transfer was calculated as the ratio between neonatal and maternal immunoglobulin G (IgG) levels.
More than 2,700 newborns were born during the study period. Of these, 130 were born to women infected with SARS-CoV-2 during pregnancy.
Peripartum infection with SARS-CoV-2 was observed in 24 dyads. Most of the babies were born vaginally, while 28 required a caesarean section.
The rate of caesarean deliveries was similar between women with and without infection. Similarly, preterm births were comparable in infected and uninfected people.
A total of 106 infants were born to mothers diagnosed with SARS-CoV-2 infection two or more weeks before delivery. Seventy-six women were symptomatic with mild disease. Fourteen asymptomatic women were identified through serological screening and were unaware of their serological status at delivery.
The remaining asymptomatic women were tested due to a history of exposure to SARS-CoV-2. No participants have been vaccinated against coronavirus disease 2019 (COVID-19).
The researchers analyzed 32 placental biopsies for viral ribonucleic acid (RNA) and noted only one positive sample. This SARS-CoV-2 positive biopsy specimen was from a study participant with mild disease eight weeks before delivery.
Newborns from the 106 mothers tested negative for SARS-CoV-2 within 24 hours of life. Mean birth weight was 3305 g, mean length was 49.8 cm, median GA was 39 weeks, and mean head circumference was 33.9 cm.
Six infants were born preterm and were therefore excluded from follow-up and serological studies. Birth defects were not detected.
Laboratory results were normal for all infants except one who had low hemoglobin. All newborns passed the hearing assessment. Additionally, cerebral and abdominal ultrasound and fundus evaluations revealed no abnormal/pathological findings.
Growth parameters remained within normal limits for all infants during the one-year follow-up. Matched neonatal and maternal serum samples within two days of delivery were available for 100 dyads.
Anti-SARS-CoV-2 immunoglobulin G (IgG) was detected in all mothers, with thirteen mothers having both IgM and IgG antibodies. Similarly, IgG antibodies against SARS-CoV-2 were detected in 96 neonates, and only one neonate had both IgM and IgG antibodies.
The rate of transplacental transfer increased significantly when maternal infection occurred in the second trimester compared to infections in the first or third trimester.
The evidence suggests that in utero transmission of SARS-CoV-2 is rare. Fetal and maternal tissue samples are needed to confirm in utero transmission.
However, researchers were unable to routinely collect these samples, limiting the ability to assess in utero transmission. Rates of preterm birth and caesarean section were comparable between infected and uninfected mothers.
Transplacental transfer ratios were higher when maternal infections occurred in the second trimester than in the first or third trimester. Additionally, maternally acquired neonatal IgG antibodies correlated with maternal IgG levels.
Overall, the study results indicate favorable clinical outcomes in all infants born to mothers infected with SARS-CoV-2 during pregnancy.
- Capretti, MG, Marsico, C., Gabrielli, L., et al. (2022). Infants born following SARS-CoV-2 infection during pregnancy. Pediatrics. doi:10.1542/peds.2022-056206