Vertical Transmission of SARS-CoV-2: A Systematic Review

COVID-19 in Pregnant Women, Maternal-Fetal Involvement, and Vertical Mother-to-Child Transmission: A Systematic Review

Pregnant women are included in the COVID-19 risk groups even if they do not have any pathology. This requires an analysis of research focused on pregnant women to understand the impact of SARS-CoV-2 on their condition. There is also a need to know whether there is vertical mother-to-child transmission, as well as other consequences in case the pregnant woman is infected and COVID-19 positive. A systematic review was carried out to analyze the existing information on the complications of a pregnant woman infected with the SARS-CoV-2 coronavirus and the possibility of vertical transmission from mother to child, registered in the PROSPERO website and searched in the PubMed, Scopus, CINAHL, and Cochrane Library databases. Finally, 22 articles were included in the review. The review suggests that vertical transmission from mother to child could be exceptionally possible at the time of delivery or breastfeeding, but not through the placenta. It is interesting to point out the good acceptance of vaccination by pregnant women, which may be the reason for the low infectivity. Further research on pregnant women should be carried out to provide evidence on vertical mother-to-child transmission and the role of breast milk in relation to SARS-CoV-2.

COVID 19 in pregnant women and neonates: Clinical characteristics and laboratory and imaging findings. An overview of systematic reviews

Introduction: SARS-CoV-2 infection in the perinatal period may be associated with an increased risk of morbidity and mortality in both the mother and the neonate. Objective: To describe the clinical characteristics and, laboratory and imaging findings in pregnant women with COVID-19 and their newborns. Materials and methods: We searched PubMed, Scopus, Web of Science, and Cochrane databases for systematic reviews published between February 1, 2020, and May 30, 2021, describing clinical characteristics and laboratory and imaging (chest) findings in pregnant women with COVID-19 and their newborns; there were no language restrictions. Data were reanalyzed by means of Bayesian meta-analysis using Markov Chain Monte Carlo methods. The study protocol is registered in PROSPERO under code CRD42020178329. Results: Six systematic reviews were retrieved (for a total of 617 primary studies). A narrative synthesis of the proportions of signs, symptoms, and imaging and laboratory findings of both mothers and neonates was performed. The Odds ratios (OR) between pregnant women with and without COVID-19 were as follows: fetal well-being involvement: 1.9 (95%CI:1.09-3.63); stillbirth: 1.73 (95%CI:1.01-2.94); preterm birth: 1.77 (95%CI:1.25-2.61); maternal admission to the intensive care unit (ICU): 6.75 (95%CI:1-31.19). Regarding symptomatology, the following OR was obtained for myalgia between pregnant women and non-pregnant women with COVID-19: 0.67 (95% CI:0.51-0.93). Conclusions: Cough, fever, dyspnea, and myalgia are the most common symptoms in pregnant women with COVID-19; in addition, there is a higher risk of admission to the ICU. Regarding complementary testing, the most frequent alterations are lymphopenia and the evidence of lesions in chest imaging studies. The presence of COVID-19 in pregnant women is associated with premature birth. It seems that SARS-CoV-2 infection in neonates is not serious and the risk of vertical transmission is low, since no data about congenital malformations attributable to the virus were found.

Effects of Vertical Transmission of Respiratory Viruses to the Offspring

Overt and subclinical maternal infections in pregnancy can have multiple and significant pathological consequences for the developing fetus, leading to acute perinatal complications and/or chronic disease throughout postnatal life. In this context, the current concept of pregnancy as a state of systemic immunosuppression seems oversimplified and outdated. Undoubtedly, in pregnancy the maternal immune system undergoes complex changes to establish and maintain tolerance to the fetus while still protecting from pathogens. In addition to downregulated maternal immunity, hormonal changes, and mechanical adaptation (e.g., restricted lung expansion) make the pregnant woman more susceptible to respiratory pathogens, such as influenza virus, respiratory syncytial virus (RSV), and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Depending on the infectious agent and timing of the infection during gestation, fetal pathology can range from mild to severe, and even fatal. Influenza is associated with a higher risk of morbidity and mortality in pregnant women than in the general population, and, especially during the third trimester of pregnancy, mothers are at increased risk of hospitalization for acute cardiopulmonary illness, while their babies show higher risk of complications such as prematurity, respiratory and neurological illness, congenital anomalies, and admission to neonatal intensive care. RSV exposure in utero is associated with selective immune deficit, remodeling of cholinergic innervation in the developing respiratory tract, and abnormal airway smooth muscle contractility, which may predispose to postnatal airway inflammation and hyperreactivity, as well as development of chronic airway dysfunction in childhood. Although there is still limited evidence supporting the occurrence of vertical transmission of SARS-CoV-2, the high prevalence of prematurity among pregnant women infected by SARS-CoV-2 suggests this virus may alter immune responses at the maternal-fetal interface, affecting both the mother and her fetus. This review aims at summarizing the current evidence about the short- and long-term consequences of intrauterine exposure to influenza, RSV, and SARS-CoV-2 in terms of neonatal and pediatric outcomes.

Placental SARS-CoV-2 distribution correlates with level of tissue oxygenation in COVID-19-associated necrotizing histiocytic intervillositis/perivillous fibrin deposition

Introduction

Recent evidence supports the – rare – occurrence of vertical transplacental SARS-CoV-2 transmission. We previously determined that placental expression of angiotensin-converting enzyme 2 (ACE2), the SARS-CoV-2 receptor, and associated viral cell entry regulators is upregulated by hypoxia. In the present study, we utilized a clinically relevant model of SARS-CoV-2-associated chronic histiocytic intervillositis/massive perivillous fibrin deposition (CHIV/MPFVD) to test the hypothesis that placental hypoxia may facilitate placental SARS-CoV-2 infection.

Methods

We performed a comparative immunohistochemical and/or RNAscope in-situ hybridization analysis of carbonic anhydrase IX (CAIX, hypoxia marker), ACE2 and SARS-CoV-2 expression in free-floating versus fibrin-encased chorionic villi in a 20-weeks’ gestation placenta with SARS-CoV-2-associated CHIV/MPVFD.

Results

The levels of CAIX and ACE2 immunoreactivity were significantly higher in trophoblastic cells of fibrin-encased villi than in those of free-floating villi, consistent with hypoxia-induced ACE2 upregulation. SARS-CoV-2 showed a similar preferential localization to trophoblastic cells of fibrin-encased villi.

Discussion

The localization of SARS-CoV-2 to hypoxic, fibrin-encased villi in this placenta with CHIV/MPVFD suggests placental infection and, therefore, transplacental SARS-CoV-2 transmission may be promoted by hypoxic conditions, mediated by ACE2 and similar hypoxia-sensitive viral cell entry mechanisms. Understanding of a causative link between placental hypoxia and SARS-CoV-2 transmittability may potentially lead to the development of alternative strategies for prevention of intrauterine COVID-19 transmission.

[Recommendations for SARS-CoV-2/COVID-19 during Pregnancy, Birth and Childbed - Update November 2021 (Long Version)]

Since the onset of the SARS-CoV-2 pandemic, the German Society of Gynecology and Obstetrics and the Society for Peri-/Neonatal Medicine have published and repeatedly updated recommendations for the management of SARS-CoV-2 positive pregnancies and neonates. As a continuation of existing recommendations, the current update addresses key issues related to the prenatal, perinatal, and postnatal care of pregnant women, women who have given birth, women who have recently given birth, women who are breastfeeding with SARS-CoV-2 and COVID-19, and their unborn or newborn infants, based on publications through September 2021. Recommendations and opinions were carefully derived from currently available scientific data and subsequently adopted by expert consensus. This guideline - here available in the long version - is intended to be an aid to clinical decision making. Interpretation and therapeutic responsibility remain with the supervising local medical team, whose decisions should be supported by these recommendations. Adjustments may be necessary due to the rapid dynamics of new evidence. The recommendations are supported by the endorsement of the professional societies: German Society for Perinatal Medicine (DGPM), German Society of Gynecology and Obstetrics (DGGG), German Society for Prenatal and Obstetric Medicine (DGPGM), German Society for Pediatric Infectiology (DGPI), Society for Neonatology and Pediatric Intensive Care Medicine (GNPI).

Vertical Transmission of SARS-CoV-2: A Systematic Review of Systematic Reviews

The COVID-19 pandemic has hugely impacted global public health and economy. The COVID-19 has also shown potential impacts on maternal perinatal and neonatal outcomes. This systematic review aimed to summarize the evidence from existing systematic reviews about the effects of SARS-CoV-2 infections on maternal perinatal and neonatal outcomes. We searched PubMed, MEDLINE, Embase, and Web of Science in accordance with PRISMA guidelines, from 1 December 2019 to 7 July 2021, for published review studies that included case reports, primary studies, clinical practice guidelines, overviews, case-control studies, and observational studies. Systematic reviews that reported the plausibility of mother-to-child transmission of COVID-19 (also known as vertical transmission), maternal perinatal and neonatal outcomes, and review studies that addressed the effect of SARS-CoV-2 infection during pregnancy were also included. We identified 947 citations, of which 69 studies were included for further analysis. Most (>70%) of the mother-to-child infection was likely due to environmental exposure, although a significant proportion (about 20%) was attributable to potential vertical transmission of SARS-CoV-2. Further results of the review indicated that the mode of delivery of pregnant women infected with SARS-CoV-2 could not increase or decrease the risk of infection for the newborns (outcomes), thereby emphasizing the significance of breastfeeding. The issue of maternal perinatal and neonatal outcomes with SARS-CoV-2 infection continues to worsen during the ongoing COVID-19 pandemic, increasing maternal and neonatal mortality, stillbirth, ruptured ectopic pregnancies, and maternal depression. Based on this study, we observed increasing rates of cesarean delivery from mothers with SARS-CoV-2 infection. We also found that SARS-CoV-2 could be potentially transmitted vertically during the gestation period. However, more data are needed to further investigate and follow-up, especially with reports of newborns infected with SARS-CoV-2, in order to examine a possible long-term adverse effect.

Current Resources for Evidence-Based Practice, July 2021

An extensive review of new resources to support the provision of evidence-based care for women and infants. The current column includes a discussion of how fetal monitoring may lead to overuse of birth-related interventions, commentaries on reviews focused on bedsharing, and women's lifetime estrogen exposure and risk of cardiovascular mortality.