COVID-19 and vertical transmission: assessing the expression of ACE2/TMPRSS2 in the human fetus and placenta to assess the risk of SARS-CoV-2 infection

The Multi-faceted Effects of COVID-19 on Female Reproductive Health: An Updated Narrative Review

Concerns about the SARS-CoV-2 pandemic's possible impact on sexual and reproductive health have grown significantly. In this narrative review, the latest research on the effects of SARS-CoV-2 infection on several facets of sexual and reproductive health is reviewed. The review starts initially by going through the possible consequences of SARS-CoV-2 on female menstrual cycles. The virus may interfere with the menstrual cycle, which could affect hormone synthesis and endometrial reactions, according to newly available evidence. Menstrual blood loss may be impacted by COVID-19's potential to influence endothelial cell function and systemic hemostasis. Hypothalamic amenorrhea may be brought on by severe COVID-19 disease. There is little research on this subject, although most women resume their regular menstrual cycles after 1-2 months of recuperation. The review also examines how SARS-CoV-2 infection may affect assisted reproductive technology (ART) treatments. There are few clinical data, although some research points to potential effects on embryo quality. Overall, ART results, however, did not materially change from the time before the epidemic. Obstetric problems are more likely when SARS-CoV-2 infection occurs during pregnancy, especially in the third trimester. Even though the maternal death rate is still low, pregnant women, especially those with comorbidities, are more likely to experience serious sickness. The review emphasizes how the COVID-19 vaccine affects menstrual cycles, showing brief, modest modifications without serious health hazards. Also included are the psychological effects of family planning choices during the pandemic. In conclusion, this narrative review offers a thorough assessment of the complicated and changing effects of SARS-CoV-2 on sexual and reproductive health. The different requirements of people and couples during and after the pandemic are highlighted, underscoring the necessity for ongoing study and specialized healthcare practices.

Analysis of the transplacental transmission of SARS CoV-2 virus and antibody transfer according to the gestational age at maternal infection

To quantify transplacental transmission of SARS-CoV-2 virus and antibody transfer in pregnant women and their newborns according to the gestational age at maternal infection. A prospective observational multicenter study including pregnant women with a positive RT-PCR or a positive serology for SARS-CoV-2 and compatible symptoms, from April to December 2020, in 11 French maternities. The study was designed to obtain a systematic collection of mother-infant dyad's samples at birth. SARS-CoV-2 viral load was measured by RT-PCR. IgG and IgM antibodies against the SARS-CoV-2 spike protein were measured by enzyme-linked immunosorbent assay. Antibody concentrations and transplacental transfer ratios were analyzed according to the gestational age at maternal infection. The primary outcome was the rate of SARS CoV-2 materno-fetal transmission at birth. The secondary outcome was the quantification of materno-fetal antibody transfer. Maternal and neonatal outcomes at birth were additionally assessed. Among 165 dyads enrolled, one congenital infection was confirmed {n = 1 (0.63%) IC95% [0.02%; 3.48%]}. The average placental IgG antibody transfer ratio was 1.27 (IC 95% [0.69-2.89]). The transfer ratio increased with increasing time between the onset of maternal infection and delivery (P Value = 0.0001). Maternal and neonatal outcomes were reassuring. We confirmed the very low rate of SARS-CoV-2 transplacental transmission (< 1%). Maternal antibody transfer to the fetus was more efficient when the infection occurred during the first and second trimester of pregnancy.

Vertical transmission and maternal passive immunity post-SARS-CoV-2

Since 2020, the highly contagious nature and various transmission routes of SARS-CoV-2 have rendered the pandemic interminable. Vertical transmission (VT) through the placenta and breast milk, which is frequent for certain virus types, is thought to exist for SARS-CoV-2 and is hypothesized by many researchers. Conversely, antibodies are produced to counteract the effect of viruses. Since newborns' immunologic system cannot produce proper antibodies, maternal antibodies are usually transferred from mother to infant/fetus to meet the need. This theory leads to the hypothesis of transmission of antibodies through the placenta and breast milk following SARS-CoV-2 infection or vaccination. This paper further discusses these hypotheses, considering consequences of fetus/infant harm versus benefit.

Diminished antiviral innate immune gene expression in the placenta following a maternal SARS-CoV-2 infection

BACKGROUND

COVID-19 is caused by the SARS-CoV-2 virus and is associated with critical illness requiring hospitalization, maternal mortality, stillbirth, and preterm birth. SARS-CoV-2 has been shown to induce placental pathology. However, substantial gaps exist in our understanding of the pathophysiology of COVID-19 disease in pregnancy and the long-term impact of SARS-CoV-2 on the placenta and fetus. To what extent a SARS-CoV-2 infection of the placenta alters the placental antiviral innate immune response is not well understood. A dysregulated innate immune response in the setting of maternal COVID-19 disease may increase the risk of inflammatory tissue injury or placental compromise and may contribute to deleterious pregnancy outcomes.

OBJECTIVE

We sought to determine the impact of a maternal SARS-CoV-2 infection on placental immune response by evaluating gene expression of a panel of 6 antiviral innate immune mediators that act as biomarkers of the antiviral and interferon cytokine response. Our hypothesis was that a SARS-CoV-2 infection during pregnancy would result in an up-regulated placental antiviral innate immune response.

STUDY DESIGN

We performed a case-control study on placental tissues (chorionic villous tissues and chorioamniotic membrane) collected from pregnant patients with (N=140) and without (N=24) COVID-19 disease. We performed real-time quantitative polymerase chain reaction and immunohistochemistry, and the placental histopathology was evaluated. Clinical data were abstracted. Fisher exact test, Pearson correlations, and linear regression models were used to examine proportions and continuous data between patients with active (<10 days since diagnosis) vs recovered COVID-19 (>10 days since diagnosis) at the time of delivery. Secondary regression models adjusted for labor status as a covariate and evaluated potential correlation between placental innate immune gene expression and other variables.

RESULTS

SARS-CoV-2 viral RNA was detected in placental tissues from 5 women with COVID-19 and from no controls (0/24, 0%). Only 1 of 5 cases with detectable SARS-CoV-2 viral RNA in placental tissues was confirmed to express SARS-CoV-2 nucleocapsid and spike proteins in syncytiotrophoblast cells. We detected a considerably lower gene expression of 5 critical innate immune mediators (IFNB, IFIT1, MXA, IL6, IL1B) in the chorionic villi and chorioamniotic membranes from women with active or recovered COVID-19 than controls, which remained significant after adjustment for labor status. There were minimal correlations between placental gene expression and other studied variables including gestational age at diagnosis, time interval between COVID-19 diagnosis and delivery, prepregnancy body mass index, COVID-19 disease severity, or placental pathology.

CONCLUSION

A maternal SARS-CoV-2 infection was associated with an impaired placental innate immune response in chorionic villous tissues and chorioamniotic membranes that was not correlated with gestational age at COVID-19 diagnosis, time interval from COVID-19 diagnosis to delivery, maternal obesity, disease severity, or placental pathology.

Transmission of SARS-CoV-2 from mother to fetus or neonate: What to know and what to do?

SARS-CoV-2 can be vertically transmitted from the mother to the fetus and the neonate. This transmission route is rare compared to the environmental or horizontal spread and therefore, the risk can be deemed inconsequential by some medical providers. However, severe, although just as rare, feto-neonatal consequences are possible: fetal demise, severe/critical neonatal COVID-19 and multi-inflammatory syndrome (MIS-N) have been described. Therefore, it is important for the clinicians to know the mechanism of vertical transmission, how to recognize this, and how to deal with neonatal COVID-19 and MIS-N. Our knowledge about this field has significantly increased in the last three years. This is a summary of the pathophysiology, diagnostics, and therapeutics of vertical SARS-CoV-2 transmission that clinicians apply in their clinical practice.

The Potential Role of Microorganisms on Enteric Nervous System Development and Disease

The enteric nervous system (ENS), the inherent nervous system of the gastrointestinal (GI) tract is a vast nervous system that controls key GI functions, including motility. It functions at a critical interface between the gut luminal contents, including the diverse population of microorganisms deemed the microbiota, as well as the autonomic and central nervous systems. Critical development of this axis of interaction, a key determinant of human health and disease, appears to occur most significantly during early life and childhood, from the pre-natal through to the post-natal period. These factors that enable the ENS to function as a master regulator also make it vulnerable to damage and, in turn, a number of GI motility disorders. Increasing attention is now being paid to the potential of disruption of the microbiota and pathogenic microorganisms in the potential aetiopathogeneis of GI motility disorders in children. This article explores the evidence regarding the relationship between the development and integrity of the ENS and the potential for such factors, notably dysbiosis and pathogenic bacteria, viruses and parasites, to impact upon them in early life.

SARS-CoV-2 Infection in Pregnancy: Clues and Proof of Adverse Outcomes

BACKGROUND

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) represents one of the most threatening viral infections in the last decade. Amongst susceptible individuals, infected pregnant women might be predisposed to severe complications. Despite the extensive interest in SARS-CoV-2 research, the clinical course of maternal infection, the vertical transmission and the neonatal outcomes have not been completely understood yet. The aim of our study was to investigate the association between SARS-CoV-2 infection, obstetric outcomes and vertical transmission.

METHODS

A prospective observational study was performed, enrolling unvaccinated pregnant patients positive for SARS-CoV-2 (cases) and matched with uninfected pregnant women (controls). Maternal and neonatal nasopharyngeal swabs, maternal and cord blood, amniotic fluid and placenta tissue samples were collected; blood samples were tested for anti-S and anti-N antibodies, and histologic examination of placental tissues was performed.

RESULTS

The cases showed a significant association with the development of some obstetric complications, such as intrauterine growth restriction and pregnancy-associated hypothyroidism and diabetes, as compared to controls; their newborns were more likely to have a low birth weight and an arterial umbilical pH less than 7. The viral genome was detected in maternal and cord blood and placental samples in six cases.

CONCLUSIONS

Pregnant women positive for SARS-CoV-2 infection are more likely to develop severe obstetric outcomes; their newborns could have a low birth weight and arterial pH. Vertical transmission seems a rare event, and further investigation is strongly needed.

A Review of Coronavirus Disease 2019 in Pregnancy

Pregnancy is an independent risk factor for morbidity and mortality in coronavirus disease 2019 (COVID-19) with increased rates of operative delivery, intensive care unit admission, and mechanical ventilation as well as a possible increased risk of death, independent of other risk factors, compared with nonpregnant women with COVID-19. Furthermore, pregnancy outcomes are worse in those with COVID-19 with increased risk for preeclampsia, venous thromboembolism, preterm birth, miscarriage, and stillbirth compared with pregnant women without COVID-19. Importantly, pregnant women of nonwhite ethnicity appear to be at greater risk of severe COVID-19, necessitating improved access to care and closer monitoring in these women. The management of COVID-19 in pregnancy is largely similar to that in nonpregnant people; however, there is an important emphasis on multidisciplinary team involvement to ensure favorable outcomes in both mother and baby. Similarly, vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is safe in pregnancy and improves maternal and neonatal outcomes.

Single-Cell Immunobiology of the Maternal-Fetal Interface

Pregnancy success requires constant dialogue between the mother and developing conceptus. Such crosstalk is facilitated through complex interactions between maternal and fetal cells at distinct tissue sites, collectively termed the "maternal-fetal interface." The emergence of single-cell technologies has enabled a deeper understanding of the unique processes taking place at the maternal-fetal interface as well as the discovery of novel pathways and immune and nonimmune cell types. Single-cell approaches have also been applied to decipher the cellular dynamics throughout pregnancy, in parturition, and in obstetrical syndromes such as recurrent spontaneous abortion, preeclampsia, and preterm labor. Furthermore, single-cell technologies have been used during the recent COVID-19 pandemic to evaluate placental viral cell entry and the impact of SARS-CoV-2 infection on maternal and fetal immunity. In this brief review, we summarize the current knowledge of cellular immunobiology in pregnancy and its complications that has been generated through single-cell investigations of the maternal-fetal interface.

Clinical Assessment of Fetal Well-Being and Fetal Safety Indicators

Delivering safe clinical trials of novel therapeutics is central to enable pregnant women and their babies to access medicines for better outcomes. This review describes clinical monitoring of fetal well‐being and safety. Current pregnancy surveillance includes regular antenatal checks of blood pressure and urine for signs of gestational hypertension. Fetal and placental development is assessed routinely using the first‐trimester “dating” and mid‐trimester “anomaly” ultrasound scans, but the detection of fetal anomalies can continue throughout pregnancy using targeted sonography or magnetic resonance imaging (MRI). Serial sonography can be used to assess fetal size, well‐being, and placental function. Carefully defined reproducible imaging parameters, such as the head circumference (HC), abdominal circumference (AC), and femur length (FL), are combined to calculate an estimate of the fetal weight. Doppler analysis of maternal uterine blood flow predicts placental insufficiency, which is associated with poor fetal growth. Fetal doppler analysis can indicate circulatory decompensation and fetal hypoxia, requiring delivery to be expedited. Novel ways to assess fetal well‐being and placental function using MRI, computerized cardiotocography (CTG), serum circulating fetoplacental proteins, and mRNA may improve the assessment of the safety and efficacy of maternal and fetal interventions. Progress has been made in how to define and grade clinical trial safety in pregnant women, the fetus, and neonate. A new system for improved safety monitoring for clinical trials in pregnancy, Maternal and Fetal Adverse Event Terminology (MFAET), describes 12 maternal and 18 fetal adverse event (AE) definitions and severity grading criteria developed through an international modified Delphi consensus process. This fills a vital gap in maternal and fetal translational medicine research.

Fetoplacental transmission and placental response to SARS-CoV-2: Evidence from the literature

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a dreadful novel coronavirus with global health concerns among pregnant women. To date, the vertical transmission of SARS-CoV-2 during pregnancy remains controversial. We briefly report recent findings of placental response to SARS-CoV-2 infection and updates on vertical transmission. We systematically searched PubMed and Google Scholar databases according to PRISMA guidelines for studies reporting the effects of SARS-CoV-2 infection on the placenta and possibility of vertical transmission. We identified 45 studies reporting 1,280 human placentas that were analyzed by molecular pathology methods and 11,112 placenta-derived cells from a publicly available database that was analyzed using bioinformatics tools. The main finding of this study is that the SARS-CoV-2 canonical entry receptors (ACE2 and TMPRSS2) are abundantly expressed on the placenta during the first trimester, and this expression diminishes across gestational age. Out of 45 eligible studies identified, 24 (53.34%) showed no evidence of vertical transmission, 15 (33.33%) supported the hypothesis of very rare, low possibility of vertical transmission and 6 (13.33%) were indecisive and had no comment on vertical transmission. Furthermore, 433 placentas from 12 studies were also identified for placental pathology investigation. There was evidence of at least one form of maternal vascular malperfusion (MVM), 57/433 (13.1%), fetal vascular malperfusion (FVM), 81/433 (18.7%) and placental inflammation with excessive infiltration of CD3+ CD8+ lymphocytes, CD68+ macrophages and CD20+ lymphocytes in most of the eligible studies. Decidual vasculopathy (3.2%), infarction (3.2%), chronic histiocytic intervillositis (6.0%), thrombi vasculopathy (5.1%) were also observed in most of the MVM and FVM reported cases. The results indicated that SARS-CoV-2 induces placenta inflammation, and placenta susceptibility to SARS-CoV-2 decreases across the pregnancy window. Thus, SARS-CoV-2 infection in early pregnancy may adversely affect the developing fetus.

Fetal Deaths in SARS-CoV-2-Infected Pregnant Women: A Portuguese Case Series

Introduction

Stillbirth has been documented as an outcome of SARS-CoV-2 infection in pregnancy. Placental hypoperfusion and inflammation secondary to maternal immune response seem to play a role in the cascade of events that contribute to fetal death. The aim of our study is to report a perinatal outcome of SARS-CoV-2 infection in pregnancy adding information to the pool of data on COVID-19 pregnancy outcomes. Case Presentation. This is the first stillbirth case series occurring in pregnant women infected with SARS-CoV-2 in a Portuguese cohort. Between April 2020 and March 2021, we had 2680 births in our centre, of which 130 (4.95%) involved mothers infected with SARS-CoV-2. Of total births, there were 14 stillbirths (0.52%), accounting for the highest stillbirth rate we have had in the last 5 years. Among these 14 stillbirths, 5 (35.71%) occurred in SARS-CoV-2-infected mothers. We report the clinical features and placental histopathologic findings of 4 stillbirth cases that occurred in our hospital. Discussion. The stillbirth rate among SARS-CoV-2-infected pregnant women (5/130; 3.84%) was significantly increased compared to noninfected patients (9/2550; 0.35%). Most women (3/4) were asymptomatic for COVID-19, a surprising outcome, given the current literature. All cases had histologic exams showing placental signs of vascular malperfusion, although we acknowledge that 3/5 had obstetric conditions related to placental vascular impairment such as preeclampsia and HELLP syndrome.

Conclusion

Stillbirth can be a perinatal consequence of SARS-CoV-2 infection in pregnancy, even in asymptomatic patients. We urge more studies to explore the association between SARS-CoV-2 infection and the risk of stillbirth.

Mast Cell Activation Syndrome in COVID-19 and Female Reproductive Function: Theoretical Background vs. Accumulating Clinical Evidence

Coronavirus disease 2019 (COVID-19), a pandemic disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, can affect almost all systems and organs of the human body, including those responsible for reproductive function in women. The multisystem inflammatory response in COVID-19 shows many analogies with mast cell activation syndrome (MCAS), and MCAS may be an important component in the course of COVID-19. Of note, the female sex hormones estradiol (E2) and progesterone (P4) significantly influence mast cell (MC) behavior. This review presents the importance of MCs and the mediators from their granules in the female reproductive system, including pregnancy, and discusses the mechanism of potential disorders related to MCAS. Then, the available data on COVID-19 in the context of hormonal disorders, the course of endometriosis, female fertility, and the course of pregnancy were compiled to verify intuitively predicted threats. Surprisingly, although COVID-19 hyperinflammation and post-COVID-19 illness may be rooted in MCAS, the available clinical data do not provide grounds for treating this mechanism as significantly increasing the risk of abnormal female reproductive function, including pregnancy. Further studies in the context of post COVID-19 condition (long COVID), where inflammation and a procoagulative state resemble many aspects of MCAS, are needed.

What is the Hidden Biological Mechanism Underlying the Possible SARS-CoV-2 Vertical Transmission? A Mini Review

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS- CoV-2) represents an emerging infection that is spreading around the world. Among susceptible patients, pregnant women are more likely to develop serious complications and negative obstetric outcomes. Vertical transmission constitutes a debating issue which has not been completely understood. This review aims at describing the currently available evidence on SARS-CoV2 vertical transmission. We carried out a computerized literature search in the Cochrane Library, PubMed, Scopus and Web of Science, selecting the most relevant studies on vertical transmission from the outbreak onset until February 2022. The analysis of the available literature identifies the presence of SARS-CoV2 genome in different biological specimens, confirming the hypothesis that a transplacental infection can occur. In spite of the high number of infected people around the world, mother-to-child infections have been infrequently reported but it can be observed under certain biologic conditions. A deep knowledge of the underlying mechanisms of SARS-CoV2 vertical transmission is of paramount importance for planning an adequate management for the affected mothers and newborns.

Monocytes and macrophages in pregnancy: The good, the bad, and the ugly

A successful human pregnancy requires precisely timed adaptations by the maternal immune system to support fetal growth while simultaneously protecting mother and fetus against microbial challenges. The first trimester of pregnancy is characterized by a robust increase in innate immune activity that promotes successful implantation of the blastocyst and placental development. Moreover, early pregnancy is also a state of increased vulnerability to vertically transmitted pathogens notably, human immunodeficiency virus (HIV), Zika virus (ZIKV), SARS-CoV-2, and Listeria monocytogenes. As gestation progresses, the second trimester is marked by the establishment of an immunosuppressive environment that promotes fetal tolerance and growth while preventing preterm birth, spontaneous abortion, and other gestational complications. Finally, the period leading up to labor and parturition is characterized by the reinstatement of an inflammatory milieu triggering childbirth. These dynamic waves of carefully orchestrated changes have been dubbed the "immune clock of pregnancy." Monocytes in maternal circulation and tissue-resident macrophages at the maternal-fetal interface play a critical role in this delicate balance. This review will summarize the current data describing the longitudinal changes in the phenotype and function of monocyte and macrophage populations in healthy and complicated pregnancies.