Placental examination
The placental tissues of Case A to D were examined which showed varying degrees of injury. Case A showed multiple placental calcifications and increased syncytiotrophoblast knot. Case B showed placental chronic infarct at the maternal side. The villous structure collapsed with fibrin deposition. The middle of the placenta was normal. Case C showed oedema in the villi and fibrosis in the 12-week-old placenta. No definite thrombosis was found. No obvious chorioamnionitis or virus inclusion body formation was observed in all cases. The umbilical cord and amnion membranes were normal (Fig.2).
Immunohistochemical staining of ACE2 showed that both the placenta and the decidual membrane expressed ACE2, which was located in the membrane and cytoplasm of the syncytiotrophoblast and decidual cells. The placental expression was strongest at 12 weeks of gestation (Fig. 3).
Placental SARS-CoV-2 nucleic acid test results of all the cases Case A,B,C,D were negative (Table 1).