RT-qPCR detection of SARS-CoV-2 RNA in placentas of women with spontaneous abortion: a retrospective pilot study

BACKGROUND: Concerns about the possible effects of SARS-CoV-2 on pregnancy have been raised because ACE2 receptors are expressed in placental cells, and previous studies have suggested potential associations with adverse outcomes such as spontaneous abortion and preterm birth. This retrospective pilot study aimed to detect SARS-CoV-2 RNA in archived FFPE placental tissues from women who experienced spontaneous abortion. METHODS: This cross-sectional study analyzed 83 paraffin blocks of placentas from mothers who had spontaneous abortions between winter 2021 and summer 2022. RNA was extracted, assessed for quality and quantity, and RT-qPCR was employed to identify the SARS-CoV-2 genome. Histopathological evaluations were also performed, with results analyzed using SPSS version 26. RESULTS: Among the 83 samples, 35 mothers (42.2%) were aged 30 to 40, with ages from 17 to 57. The most common symptom was bleeding (57.83%). Maternal SARS-CoV-2 test returned negative for 73 (87.9%) and positive for 10 (12.1%). Half of the abortions occurred in the first trimester, and 25.3% of mothers had hypertension, while 9.6% had hyperthyroidism. Three placental samples (3.6%) tested positive for SARS-CoV-2 RNA and exhibited histopathological findings consistent with the placentitis triad previously reported in SARS-CoV-2-associated cases. CONCLUSION: In this retrospective pilot study, SARS-CoV-2 RNA was detected in 3.6% of archived FFPE placental tissues from spontaneous abortion cases, and all positive samples showed histopathological features consistent with the placentitis triad described in previous reports. However, given the small number of positive cases and the limitations of the study design, these findings should be considered descriptive and hypothesis-generating, and no causal relationship can be inferred. Further prospective studies with larger cohorts are needed to clarify the relationship between SARS-CoV-2 infection and pregnancy outcomes.