Researchers report possible vertical transmission of SARS-CoV-2 in China
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A neonate born to a mother infected with SARS-CoV-2 at a hospital in Wuhan, China, had elevated levels of immunoglobuin M, or IgM, and immunoglobulin G, or IgG, antibodies and abnormal cytokine test results 2 hours after birth, suggesting that the newborn was infected in utero, researchers reported in JAMA.
At 2 hours of age, the neonate’s SARS-CoV-2 IgG level was 140.32 AU/mL, and their IgM level was 45.83 AU/mL, the researchers wrote. Cytokines were elevated (interleukin-6, 28.26 pg/mL; interleukin-10, 153.60 pg/mL), and white blood cell count was 18.08 x 109/L. A chest CT was normal.
According to the paper, results from five real-time RT-PCR reaction tests on nasopharyngeal swabs taken between 2 hours and 16 days of age were all negative. At 16 days, the infant’s IgM and IgG levels were still elevated.
“Although infection at delivery cannot be ruled out, IgM antibodies usually do not appear until 3 to 7 days after infection and the elevated IgM in the neonate was evident in a blood sample drawn 2 hours after birth,” the researchers wrote.
IgG antibodies, unlike IgM antibodies, can be transmitted to the fetus through the placenta and appear later than IgM antibodies. The elevated IgG level may reflect maternal or infant infection.
The mother’s vaginal secretions tested negative for SARS-CoV-2, the researchers reported.
According to a second letter in JAMA, neonatal throat swabs and blood samples from newborns born from six pregnant women with confirmed COVID-19 at another hospital in Wuhan all tested negative via RT-PCR, but all six infants had antibodies against SARS-CoV-2 in neonatal blood sera samples.
According to the letter, all six mothers delivered via cesarean section in negative pressure isolation rooms while wearing protective masks. The infants were isolated from their mothers immediately after delivery. As of March 8, none of the infants were presenting symptoms.
Both studies were limited by small sample sizes. A previous report showed no vertical transmission among nine infants in China born to mothers with COVID-19. – by Ken Downey Jr.
References:
Dong L, et al. JAMA. 2020; doi:10.1001/jama.2020.4621.
Zeng H, et al. JAMA. 2020; doi:10.1001/jama.2020.4861.
Disclosures: The authors report no relevant financial disclosures.
Perspective
Back to TopDavid A. Kaufman, MD
COVID-19 infections occur in pregnant women, and the question of vertical transmission and how it may potentially affect that infant in utero and after birth is being explored. A few case reports have documented COVID-19 infection in newborns in the first days after birth, but the timing of the transmission is still being studied.
There are two recent studies describing the detection of SARS-CoV-2-specific IgM in the infant’s born to mothers with COVID-19. IgM antibody doesn’t cross the placenta, so it can only be produced by the infant, but because the COVID-19 virus was not detected in these infants, it is possible the detection of IgM could be a false-positive IgM result. The test could be reacting to something different than the actual virus. This has often been the case in other IgM testing for congenital infections.
More study needs to be done to figure out if vertical transmission in utero is happening and its affects for the pregnancy and infant. There are some data suggesting that the newborn’s immature immune system may be both preventing them from being infected because of how COVID-19 invades the host as well as protecting them from having severe sequelae from the infection.
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