A new report of mother-to-fetus transmission of SARS-CoV-2 through umbilical cord blood adds to a small but growing body of evidence that the virus can be transmitted in utero.
Further,
The data
In a report published in the Journal of The Pediatric Infectious Diseases Society, Isabelle Von Kohorn, MD, PhD, of Holy Cross Health in Silver Spring, Md., and colleagues, described a case of neonatal infection with SARS-CoV-2 in a boy delivered by C-section at 34 weeks to a mother diagnosed with COVID-19 some 14 hours before. The newborn was immediately removed to a neonatal ICU and reunited with his mother a week later, once the mother had recovered.
Dr. Von Kohorn and colleagues reported that, while the infant’s nasopharyngeal swab test for SARS-CoV-2 was negative at 24 hours after birth, repeat molecular tests (using different assays) from 49 hours on were positive and indicated an increasing viral burden, although the infant never developed symptoms of COVID-19. In addition to being found in the nasopharynx, viral RNA also was detected in cord blood and in urine. No viral RNA was found in the placenta.
The circumstances of the birth, and the care taken to keep mother and her infant at a safe distance along with masking of the mother, made it “extremely unlikely” that the infant acquired his infection by the respiratory route, Dr. Von Kohorn and colleagues wrote.
“While we cannot rule out microscopic maternal blood contamination of cord blood in this or any other delivery, cord blood collection procedures are designed to avoid gross contamination with maternal blood. Microscopic contamination would not explain the RNA levels observed in our patient’s cord blood,” they wrote.
Clinicians should note that a neonate born to a mother with COVID-19 may take time to test positive for SARS-CoV-2 , the investigators argued, though the current recommendation of the American Academy of Pediatrics is to test nasopharyngeal secretions of well newborns at 24 and 48 hours but not again in the absence of symptoms. “This case suggests that some cases of SARS-CoV-2 in newborns may be detectable only after 48 hours of life.”
The authors hypothesized that virus transmitted by cord blood “seeded the nasopharynx and required 2 days for incubation and replication sufficient for detection.”
Some perspective
In an interview, Andrea Edlow, MD, A maternal-fetal medicine specialist at Massachusetts General Hospital in Boston, called the findings provocative if not definitive in establishing in utero or vertical transmission of SARS-CoV-2 in the same way that a Nature Communications case report did in July 2020. In that case, of a baby born to a mother with COVID-19, virus was seen at high levels in the placenta.
With the current case, “the absence of detectable virus in the placenta is certainly inconsistent/confusing if the authors claim hematogenous spread from mother to baby,” Dr. Edlow commented, “but the authors do offer plausible explanations, such as examination of limited areas within the placenta (when we know infection is likely to be patchy) and possible degradation of RNA prior to attempting to measure placental viral presence.”
Dr. Von Kohorn and colleagues’ study was funded by the National Institutes of Health, and the investigators disclosed no financial conflicts of interest. Dr. Edlow had no relevant financial disclosures.
SOURCE: Von Kohorn I et al. J Pediat Inf Dis Soc. 2020 Oct 22. doi: 10.1093/jpids/piaa127