The Effects of COVID-19 on the Placenta During Pregnancy.

Coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a global pandemic. The virus primarily affects the lungs where it induces respiratory distress syndrome ranging from mild to acute, however, there is a growing body of evidence supporting its negative effects on other system organs that also carry the ACE2 receptor, such as the placenta. The majority of newborns delivered from SARS-CoV-2 positive mothers test negative following delivery, suggesting that there are protective mechanisms within the placenta. There appears to be a higher incidence of pregnancy-related complications in SARS-CoV-2 positive mothers, such as miscarriage, restricted fetal growth, or still-birth. In this review, we discuss the pathobiology of COVID-19 maternal infection and the potential adverse effects associated with viral infection, and the possibility of transplacental transmission.

The road (not) taken - Placental transfer and interspecies differences.

Species differences are among the main reasons for the high failure rate of preclinical studies. A better awareness and understanding of these differences might help to improve the outcome of preclinical research. In reproduction, the placenta is the central organ regulating fetal exposure to a substance circulating in the maternal organism. Exact information about placental transfer can help to better estimate the toxic potential of a substance. From an evolutionary point of view, the chorioallantoic placenta is the organ with the highest anatomical diversity among species. Moreover, frequently used animal models in reproduction belong to rodents and lagomorphs, two groups that are characterized by the generation of an additional type of placenta, which is crucial for fetal development, but absent from humans: the inverted yolk sac placenta. Taken together, the translatability of placental transfer studies from laboratory animals to humans is challenging, which is supported by the fact that numerous species-dependent toxic effects are described in literature. Thus, reliable human-relevant data are frequently lacking and the toxic potential of chemicals and pharmaceuticals for humans can hardly be estimated, often resulting in recommendations that medical treatments or exposure to chemicals should be avoided for safety reasons. Although species differences of placental anatomy have been described frequently and the need for human-relevant research models has been emphasized, analyses of substances with species-dependent placental transfer have been performed only sporadically. Here, we present examples for species-specific placental transfer, including that of nanoparticles and pharmaceuticals, and discuss potential underlying mechanisms. With respect to the COVID 19-pandemic it might be of interest that some antiviral drugs are reported to feature species-specific placental transfer. Further, differences in placental structure and antibody transfer may affect placental transfer of ZIKA virus.

Investigating the risk of maternal-fetal transmission of SARS-CoV-2 in early pregnancy.

INTRODUCTION: The possibility of vertical transmission of SARS-CoV-2 from the mother to the fetus is one of the most crucial issues regarding the COVID-19 effects on pregnancy. In this study, we aimed to explore the risk of maternal-fetal transmission before 24 weeks of gestation, through analysis of abortion materials collected from PCR-positive women with pregnancy loss. To the best of our knowledge, apart from case reports, this study is the first prospective work on the vertical transmission of SARS-CoV-2 in early pregnancy. METHODS: The patients who had attended our clinic with the diagnosis of pregnancy loss before 24 weeks of gestation were screened for COVID-19. Vertical transmission in PCR-positive women was assessed through the presence of SARS-CoV-2 RNA in fetal-placental tissues by rt-PCR test. RESULTS: 24 of 210 (%11,4) pregnant women participating in the study had positive rt-PCR results. Placenta and curettage material samples of these PCR-positive patients were analyzed and all valid test results (21 samples) were negative for SARS CoV-2 RNA. In three cases, the rt-PCR results were invalid due to failed internal controls. DISCUSSION: In the literature, the possibility of intrauterine vertical transmission of SARS-CoV-2 is still controversial. The findings of the present study did not reveal any evidence of vertical transmission of SARS-CoV-2 in early pregnancy.

Transplacental transmission of SARS-CoV-2 infection.

SARS-CoV-2 outbreak is the first pandemic of the century. SARS-CoV-2 infection is transmitted through droplets; other transmission routes are hypothesized but not confirmed. So far, it is unclear whether and how SARS-CoV-2 can be transmitted from the mother to the fetus. We demonstrate the transplacental transmission of SARS-CoV-2 in a neonate born to a mother infected in the last trimester and presenting with neurological compromise. The transmission is confirmed by comprehensive virological and pathological investigations. In detail, SARS-CoV-2 causes: (1) maternal viremia, (2) placental infection demonstrated by immunohistochemistry and very high viral load; placental inflammation, as shown by histological examination and immunohistochemistry, and (3) neonatal viremia following placental infection. The neonate is studied clinically, through imaging, and followed up. The neonate presented with neurological manifestations, similar to those described in adult patients.