Prenatal MRI gathers insights on SARS-CoV-2 infection-induced abnormalities

February 02, 2023 | Histopathology

In assessing the effects of SARS-CoV-2 infection throughout pregnancy, past prenatal studies have relied on examining the histopathology of placentas and fetal structures. As is the case, SARS-CoV-2 enters the placental tissue by docking to the highly expressed angiotensin-converting enzyme 2 (ACE2) in fetal placental vessels and stromal cells in the decidua. But, studies regarding on how various SARS-CoV-2 variants affect fetuses are still scant. 

Compared to pathological workup which only shows end-stage placental development ex vivo, fetal MRI detects specific structural or placental aberrations earlier at the prenatal stages of development. A non-invasive diagnostic tool, this procedure can especially present the visual impact of SARS-CoV-2 on fetal development and can aid in detecting potential COVID-related pathologies in fetuses and placentas.

Published in The Lancet Regional Health-Europe, a prospective case-control study utilized prenatal MRI on 38 pregnant women with COVID-19 who were referred by two obstetric centers in Vienna, Austria. A control group comprised of 38 non-infected pregnant women was matched 1:1 based on gender, gestational age ( ±6 days), and MRI scanner field strength. Pathohistological assessment of the placenta and vaccination status of the pregnant females were closely monitored by the researchers. The infecting COVID variant was also identified through genome sequencing, RT-PCR, and the time of the infection. 

Odoo text and image block
Odoo text and image block

Out of the 38 cases of pregnant women with COVID, 20 had infections from pre-Omicron while 18 had infections from the Omicron subvariant. Prenatal MRI detected abnormalities in the form of globular placenta caused by both subvariants. However, pre-Omicron variant infections were more severe on placental functions, most likely from the low pathogenicity of Omicron. Moreover, there was an observable increased incidence of FGR with the pre-Omicron variant, a finding that is consistent with the study results of Stoecklein where there is reduced fetal lung volume after infection. Pre-Omicron infected women also have significantly thickened placentas with more frequent lobules and hemorrhages. Furthermore, three fetuses showed organ abnormalities in the liver and brain, which emphasized the pathophysiological vascular component of SARS-CoV-2 infections during pregnancy.

Hence, all pregnant women should be MRI screened for a close morphological examination of the placenta after contracting COVID-19, especially females infected with pre-Omicron variants where COVID-19-related morbidity of the fetus is more pronounced.   

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