key: cord-0811283-2cv46b9v
authors: Hijona Elósegui, Jesús Joaquín; Carballo García, Antonio Luis; Fernández Risquez, Ana Cristina
title: Reply()
date: 2021-04-30
journal: Med Clin (Engl Ed)
DOI: 10.1016/j.medcle.2021.04.002
sha: a726c01fa5b83e5b33a4d9eed07a577ba6df46a6
doc_id: 811283
cord_uid: 2cv46b9v

nan

First of all, we would like to thank Drs. Jianghui Cai, Yingzi Zhang and Mi Tang for their interest in our paper, 1 recently published in your prestigious magazine, as well as their kind comments on it, concerning which we would like to make the following observations:

1. We fully agree with our Chinese colleagues that the concept of vertical transmission of pathogens includes the transfer of such microorganisms during pregnancy, delivery or even in the postpartum period, and we apologise if the title of our paper is misleading, as the reference to "possible vertical transmission during pregnancy" may not have made sufficiently clear that our intention was not to assess the possible transfer of SARS-CoV-2 during delivery and the neonatal period, but only and exclusively during gestation. 2. We also fully agree that it is advisable to extend the study of the possible presence of coronavirus to different levels, using different maternal biological samples, but we must take into consideration that this sometimes involves invasive techniques that are not free of both maternal and foetal risks, and that in no case can they be justified for exclusive research purposes. 3. Obviously, the best evidence for a possible intrauterine transmission of SARS-CoV-2 would be the confirmation of its presence and replication in foetal lung tissue, but this is technically unfeasible. For this reason, we consider that placenta, amniotic fluid and/or cord blood viral isolations are indirect, but relatively reliable indicators of possible congenital transmission, provided that these samples are collected during pregnancy or immediately after delivery and when sampling has been carried out in conditions that minimise the inevitable risk of contamination. 2 4. On the other hand, it is well known that histological examination of placentas of women affected by COVID-19 in the peripartum usually reveals the presence of viral particles in the thickness of the placenta, as well as areas of hypoperfusion and inflammation. The scarcity of placental co-expression of ACE-2 and TMPRSS2, 2 receptors involved in the cytoplasmic entry of SARS-CoV-2, could explain their relative insensitivity to transplacental infection, but even so, we do not know whether viral interactions can use membrane receptors other than those mentioned, so the susceptibility of the tissue to transplacental infection could be broader than what is currently known. 5. Finally, and in relation to the extremely interesting contribution of Dr. Alexandre J. Vivanti, 3 we consider it important to point out that: -In his article there is no clear description of the method used by the author to obtain samples of amniotic fluid and cord blood during caesarean section. -It does not seem unlikely that inadvertent contamination of the maternal/neonatal samples could have occurred, taking into account that these were obtained in a hospital setting with patients admitted for COVID-19, that the caesarean section was performed using general anaesthesia with maternal orotracheal intubation and that the neonate was also subjected to orotracheal intubation. Unquestionably, neonatal viral isolation in the postpartum period, regardless of how early it may have been, does not allow horizontal transmission to be ruled out. 4 -An important gap in our current knowledge of COVID-19 is precisely whether its severity can condition perinatal transmission rates and, if so, the prognosis of infected newborns.

We do not want the above to be interpreted as a negationist criticism of Dr. Vivanti's brilliant contributions, 3 as his information will be of great help to us in future research on the subject. The recent emergence of COVID-19 makes almost any conclusions about the infection provisional at this stage, and it will take time and close observation of future cases to clarify the true magnitude of the disease during pregnancy.

New evidences that discard the possible vertical transmission on SARS-CoV-2 during pregnancy. Letter to the editor

Mechanisms and evidence of vertical transmission of infections in pregnancy including SARS-CoV-2

Transplacental transmission of SARS-CoV-2 infection

Infección por SARS-CoV-2 en el embarazo y posibilidad de transmisión al neonato: una revisión sistemática