To the Editors:
Chen and colleagues1 report that there is no evidence currently for intrauterine infection caused by vertical transmission in women who develop coronavirus disease 2019 (COVID-19) pneumonia in late pregnancy in The Lancet. However, we believe that the existing data are not enough to support this conclusion. Furthermore, Rasmussen and colleagues2 also reported in the American Journal of Obstetrics & Gynecology that it is unknown whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can be transmitted from the mother to the fetus.2
The 2019 novel coronavirus (2019-nCoV) is considered as SARS-CoV-2 owing to the similar structure to the SARS-CoV. There is a possibility that the 2019-nCoV can be distributed to the entire body via the circulatory system. Furthermore, the 2019-nCoV potentially works by binding to the angiotensin-converting enzyme 2 (ACE2) receptor, which was previously proven by the Anat Levy group that the placentas constitute important sources of ACE2 during pregnancy.3 We hypothesize that the 2019-nCoV is able to target the placenta directly by inducing viremia to infect the fetus through maternal-fetal vertical transmission. In addition, immunoglobulin M (IgM)-capture enzyme-linked immunosorbent assay (ELISA) provides an earlier and more efficient approach to the definite diagnosis of viral infection than RNA-based molecular tests.4 Combining these 2 methods may improve the accuracy to confirm neonatal infection.
To confirm the assumption of no intrauterine vertical transmission of SARS-CoV-2 infection, the researchers should first confirm viremia and then quantify the load of virus in the blood. Concurrently, the RNA-based molecular tests should be used in the placenta and along with quantitative analysis of ACE2 expression to determine whether the virus interacts directly with placental tissue. The combination of RNA-based molecular tests and IgM-capture ELISA should be applied to diagnose infection in cord blood, gastric swab, rectal swab, and throat swab after the neonates are born.
Because of the 2019-nCoV outbreak, pregnant women may suffer severe obstetrical outcomes after 2019-nCoV infection. Therefore, more rigorous evidence should be provided to verify the potential vertical transmission of the virus to prevent the spread of infection and to improve the obstetrical outcomes.
Footnotes
The authors report no conflict of interest.
This work was supported by a research grant from New Coronary Pneumonia Special Project of Changsha Science and Technology Department Hunan Province China (kq2001051).
References
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