SARS-CoV-2 infection during pregnancy: clinical characteristics and vertical transmission in a referral hospital in Peru

ABSTRACT The aim of this study was to analyze the vertical transmission of SARS-CoV-2 in pregnant women with COVID-19 in the Gynecology and Obstetrics Department of the Edgardo Rebagliati Martins National Hospital (HNERM). Twelve pregnant women who met the inclusion criteria were included. Real-time PCR (RT-PCR) tests for SARS-CoV-2 were performed when each woman was admitted to the hospital, placenta samples were collected for pathological evaluation as well. The results showed that vertical transmission of the virus was rare, with an overall low positivity rate in newborns. Although the study has limitations, such as the small number of cases and the lack of electron microscope analysis, it is the first attempt to evaluate vertical transmission in Peru. It is concluded that more research is needed to better understand the relationship between COVID-19 infection and complications during pregnancy.


INTRODUCTION
The COVID-19 pandemic continued to exert a significant impact worldwide during the first week of February 2022, with a total of 490 million confirmed cases and more than 5.8 million deaths.Peru was one of the countries most affected by this disease, with more than 3.3 million confirmed cases and almost 207,000 deaths (1) .Several studies have shown that SARS-CoV-2 infection can cause multisystemic involvement in pregnant women, with complications ranging from premature birth to maternal death (2) .In Peru, as in other parts of the world, CO-VID-19 has had a significant impact on maternal health care.There was a 12% increase in maternal deaths during 2021 compared with 2020, and one in nine of these deaths was related to COVID-19 (3) .The most common complications were premature rupture of membranes and preeclampsia, while 14% of newborns presented conditions such as prematurity, low birth weight, sepsis, and pneumonia (4) .
During pregnancy, physiological changes occur that make pregnant women an at-risk population (5,6) .COVID-19 can have serious repercussions in pregnant women.In addition, although vertical transmission of coronavirus is a rare event (7) , problems related to this transmission are emerging (8) .Viremia was present in 1% of adult patients showing symptoms of coronavirus dihttps://doi.org/10.17843/rpmesp.2024.412.13293 Motivation for the study.There is a gap in knowledge about vertical transmission of SARS-CoV-2 and its implications for maternal and neonatal health, despite evidence of multisystem involvement in pregnant women with COVID-19.
Main findings.The study results suggest low incidence of vertical transmission during pregnancy, with only one PCRpositive case in the placenta and one asymptomatic neonate.

Implications.
Our results can inform strategies for prevention and management of COVID-19 in pregnant women, as well as guide the development of health policies aimed at protecting maternal and neonatal health during the pandemic.

KEY MESSAGES
sease in 2019 (9) .Perinatal exposure, type of delivery, and time from delivery to diagnosis of neonatal infection are considered to determine whether infection occurred congenitally or perinatally.Newborns with coronavirus infection are usually asymptomatic (9) .
There is very little evidence of intrauterine transmission from mother to fetus or intrapartum transmission from mother to newborn.In cases of late maternal infection, the possibility that the newborn is actively infected and thus at risk for complications should be considered, as well as the possibility that the infant poses risks to health care workers.In this article, we focused on newborns whose mothers had documented or suspected COVID-19 at the time of delivery (6,10,11) .Therefore, this study aimed to analyze the vertical transmission of SARS-CoV-2 in pregnant women with COVID-19 at the Edgardo Rebagliati Martins National Hospital (HNERM).

Design and setting
This was a descriptive study that was conducted in the Department of Gynecology and Obstetrics at HNERM between January 2021 and January 2022.

Population
The study included pregnant women admitted to HNERM who met the following inclusion criteria: clinical and/or radiological and/or laboratory suspicion of SARS-CoV-2 infection and any indication for termination of pregnancy by cesarean section in the second and third trimester.Participants signed an informed consent form.Patients who had had an abortion and/or were in the first trimester of gestation were excluded from the study, as well as those who did not give their consent to participate.Twelve pregnant women met the selection criteria.

Study variables
The independent variable was the degree of severity of CO-VID-19 infection during pregnancy; cases were classified as proposed in Wuhan: moderate (mild pneumonia without acute respiratory failure or inflammatory response), severe (pneumonia with acute respiratory failure, inflammation or hypercoagulability) and critical (with criteria for intubation and invasive ventilation, shock or multiorgan failure).
The study variables, their categories and units of measurement are shown in Table 1.Data were collected on a single chart for each patient at a single time interval for subsequent analysis.

Data source/measurement and procedure
Real-time PCR (RT-PCR) diagnostic testing for SARS-CoV-2 was performed at admission of each pregnant woman by obtaining nasal swab samples from the pregnant woman, nasal swab samples from the neonate within 72 hours, placental membrane, amniotic fluid, and cord blood swab samples.Placenta samples were obtained for later microscopic evaluation.
For membrane swabbing and cord blood collection, placental swabs (placental PCR) were obtained from the amniotic (fetal) surface after clearing the surface of maternal blood and were collected from the space between the amnion and chorion after careful manual separation of the membranes.
For cord blood samples, plasma was extracted and stored at -80 °C until processing.Regarding pathological anatomy, microscopic placental findings were classified as acute inflammatory pathology corresponding to stages of maternal and fetal inflammation with neutrophil infiltrate (histological chorioamnionitis and umbilical arteritis); and chronic inflammatory pathology: lymphocyte and histiocyte infiltrate (chronic lymphocytic villitis and chronic deciduitis with plasma cells).The Amsterdam Consensus (12) was used for defining chronic intervillous villitis: low grade (less than 10 villi affected per focus or microscopic view and multifocal if found in several slides); and, high grade (greater than 10 villi in any field, it can be patchy or diffuse, if more than 30% of the parenchyma is affected).

Statistical analysis
The data were transferred to a MS Excel spreadsheet for coding and entry into the STATA program version 16.0 for Windows for statistical analysis.Since this was a descriptive study, the data were double coded and error corrected.For quantitative variables, normality was evaluated with the Shapiro-Wilk test and the mean and standard deviation or median and interquartile range were used, according to their distribution.

Ethical aspects
Before starting the study, each participant was asked to sign an informed consent form.The study did not present risks for the patients.Strict biosafety protocols were followed during sample collection, processing and transfer.The study

Maternal-perinatal outcomes
The characteristics of the study participants are presented in Table 2. Of the twelve pregnant women included, eleven were singleton pregnancies and one was a twin.Among the symptoms of the pregnant women, one had odynophagia, two had chest pain, two had nasal flaring, four had fever, seven had dyspnea and eight had cough.Nine had a positive molecular PCR test for SARS-CoV-2 and three were included due to clinical, radiological and antigenic test results compatible with COVID-19.Two cases of SARS-CoV-2 infection were severe and four critical cases were admitted to the intensive care unit (ICU).All patients underwent cesarean section.There was one positive case of SARS-CoV-2 in an asymptomatic neonate.
Regarding maternal comorbidity, we found one case of urosepsis, one of obesity, one of anemia and nine did not have comorbidities.Of the thirteen newborns born between 28 and 39 weeks, three went to the NICU and one died in utero.One 28-week fetal death was reported whose mother had severe disease (COVID-19 pneumonia, Acinetobacter baumannii bacterial infection, reactive PB thrombosis).The fetal death had negative PCR for SARS-CoV-2.The neonatal discharge diagnoses were the following: three with jaundice, four with adequate gestational age, one with low birth weight and one large for gestational age (Table 3).

Anatomopathological results
Twelve placentas were studied and eleven were by sections of placental parenchyma, umbilical cord and membranes plus one total chorionic-biamniotic twin placenta (with umbilical cords and membranes).There were three cases of pla-centas with chorangiosis and hypervascularization (25%).
We found more than ten capillaries per chorionic villus in chorangiosis cases, the etiology of which is frequent in preeclampsia.We found some foci of mild acute vellitis in 25% of placentas.Only one case had foci of immaturity of some chorionic villi.We also found alterations of the vascular epithelium, mild inflammatory congestion and some capillary vessels with thrombosis and hemorrhage in one case.The acute inflammatory infiltrate was mild in some chorionic villi (Figure 1).  a mortality rate of 30-50% and an ICU admission rate of approximately 50% in neonates (13) .
Algarroba (14) , Penfield et al. (15) and Pulinx et al. (16) reported cases in which placental tissue, membranes and amniotic fluid were tested for SARS-CoV-2 with positive results; our study detected only one positive result in placental tissue.
On the other hand, six pregnant women presented pneumonia (50%) and required admission to the ICU and about 33% required mechanical ventilation, which is similar to the findings by Dong et al. (17) .The rate of severe pneumonia  (10,11) , with a single case of positive PCR in the placenta and a single asymptomatic positive case in a neonate, the overall SARS-CoV-2 positivity rate in newborns born to infected mothers was low (<1%).

DISCUSSION
Focal chorangiosis and SARS-CoV-2 infection were detected.In our study, three neonates (25%) required intensive https://doi.org/10.17843/rpmesp.2024.412.13293 reported was similar to other studies, ranging from 0% to 46%.The increased and higher expression of this receptor on the plasma membrane of angiotestin-converting enzyme 2 (ACE2) upon binding to the viral spike protein in the second trimester of pregnancy would increase the possibility of vertical transmission of the virus (18) .It is possible that viral infection leads directly to placental disease, or that there is a common underlying cause for both placental lesions and susceptibility to SARS-CoV-2 (19) .
We found three cases with chronic placental inflammatory process, but none of high grade.Although this represents an overall frequency of 15%, there was only one case of chronic inflammation of the villi (VUE, not gradable).
Previous studies include only case reports identifying one chronic inflammatory process and three intervillitis; one of our cases had intervillitis, but it was not confirmed in other described series (20) .
Our study has some limitations.One of the main limitations is that HNERM is a referral hospital, so the patient characteristics could differ from those at other levels of care; therefore, our results should be extrapolated with caution.
Then, the limited number of cases does not allow generalizations to be made.We were unable to perform electron microscopic analysis in order to achieve a more sensitive detection of SARS-CoV-2 in the placenta.However, this is the first study in Peru to evaluate vertical transmission using PCR testing, the gold standard for SARS-CoV-2 detection.
In conclusion, vertical transmission of COVID-19 from mother to fetus is uncommon.Although one case was detec-ted in a neonate, the frequency of vertical transmission was low, suggesting a low incidence of transmission during pregnancy.Further research is needed to better understand the relationship between infection and placental complications during pregnancy.
-2 was performed by RNA extraction from biological samples with Sbeadex livestock kit reagent (LGC Biosearch Technologies) on oKtopure automated platform and molecular detection through amplification of the virus RdRp gene and RNAse P as internal control with the Logix Smart SARS-CoV-2 test kit from Co-Diagnostics Inc on Cobas Z 480 (Roche) or CoDx-Box (Biomolecular Systems) thermal cyclers.Placentas were formalin-fixed and embedded in kerosene, stained with hematoxylin/eosin stain.Immunohistochemistry with CD34 was also performed.https://doi.org/10.17843/rpmesp.2024.412.13293 was evaluated and approved by the Research Ethics Committee Specialized in COVID-19 of Essalud.(Resolution N°42-IETSI-ESSALUD 2020 dated March 27, 2020) and PRISA code No. EI00001364.

Figure 1 .
Figure 1.Placental microscopy results.A: numerous blood vessels in the chorionic villi with areas of thrombosis and syncytial knot proliferation.B: chorangiomatosis proliferation of capillaries.C: chorangiomatosis.D: Immunohistochemical staining with CD34.E: CD34 shows staining of capillary vessel walls.F: Immunohistochemistry with positive CD34 shows staining of dilated blood vessels.

Table 1 .
Maternal characteristics of patients included in the study (n=12).

Table 2 .
Maternal characteristics of patients included in the study (n=12).
There was one case of a symptomatic but COVID-19 negative woman, whose placenta had PCR for SARS-CoV-2 and showed cord with thrombi, acute vellitis and intervellitis in mild amount, intervillous and perivillous hyaline degeneration, congestion and intervillous vascular hemorrhage.ICU: intensive care unit; LDH: lactate dehydrogenase; CRP: C-reactive protein; TGO: oxaloacetic transaminase; SBP: systolic blood pressure; DBP: diastolic blood pressure.

Table 3 .
Characteristics of each case included.