Review The Effects of COVID-19 on Placenta and Pregnancy: What Do We Know So Far? Yin Ping Wong 1,*, Teck Yee Khong 2 and Geok Chin Tan 1,* 1 Department of Pathology, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Yaacob Latif, Bandar Tun Razak, 56000 Kuala Lumpur, Malaysia 2 Department of Pathology, SA Pathology, Women’s and Children’s Hospital, North Adelaide SA 5006, Australia; [email protected] * Correspondence: [email protected] (Y.P.W.); [email protected] (G.C.T.); Tel.: +60-391-455-364 (Y.P.W); +60-391-455-362 (G.C.T) Table 1. Summary of Reports on Clinical Characteristics of SARS-CoV-2 included Studies. Mum tested Number of Placenta Sent for Ultrastructural Authors Clinical History COVID-19 Placental Morphological Features IHC/ISH Findings Fetal Outcomes * Cases SARS-CoV-2 Features Positive 40y/o G3P2, 28 + 4wks’ Gross: 271 g (75–90th percentile) Virions in gestation with sepsis RT-PCR, IHC, Histo: mature chorionic villi with (IHC) +ve SARS-CoV-2 syncytiotrophobl ** Algarroba et al. 6 days prior BW: 1340 g. 1 pneumonia secondary to TEM focal villous oedema, an area of glycoprotein on placental ast, microvillus 2020 [16] delivery Neonate tested -ve severe COVID-19. Delivered (All +ve) decidual vasculopathy on cells and cell process via CS maternal surface of fibroblasts One placenta (38 + 4wk’ gestation) 27 + 4 to 38 + 4wks’ gestation, 2 3 cases +ve on BW: NA. sent for histology. Algeri et al. 2020 [17] 5 out of 5 with severe COVID-19 admission, 2 Not tested NA NA All neonates tested Histo: no sign of Delivered via 4CS, 1VD cases +ve PP -ve infection/inflammation Signs of MVM: infarction (n = 2), accelerated villous maturation (n = 4), intervillous thrombosis (n = 1). Signs of FVM: thrombi in fetal circulation (n = 3), intramural BW: 2072–4115 g, 16–41y/o, 32 + 2–40 + 4wks’ fibrin (n = 7), chorangiosis (n = 1), Baergen and Heller 20 All +ve, SGA (n = 2) gestation.Delivered via 5CS, Not tested VSK (n = 3), avascular villi (n = 3) NA NA 2020 [18] (1 twins) Unclear when All neonates tested 15VD Inflammation: chorioamnionitis (n -ve = 1), chronic villitis (n = 4), fetal vasculitis (n = 2). Others: meconium (n = 7), cord abnormalities (n = 2), chorionic cysts (n = 1) Diagnostics 2021, 11, 94. https://doi.org/10.3390/diagnostics11010094 www.mdpi.com/journal/diagnostics Diagnostics 2021, 11, 94 2 of 7 Stillbirth, BW: NA. Autopsy: no Neutrophils and monocytes in the 28y/o G1P0, 19wks gestation, malformation, ** Baud et al. 2020 2 days prior RT-PCR subchorial space, increased 1 with fever in imminent labour. NA NA Neonate, cord [19] delivery (+ve) intervillous fibrin deposition, and Delivered via VD blood and AF funisitis. tested –ve Increased intervillous and/or subchorionic fibrin deposition (n = 23, 32 and 34y/o, 3) Umbilical cords Chen S et al. 2020 1, 2 and 4 days RT-PCR 3 35–38 + 6wks’ gestation.All Increased in villous syncytial NA NA and neonates all [20] PP (-ve) delivered via CS nodules (n = 2) tested -ve Massive infarction (n = 1) Chorionic haemangioma (n = 1) No significant pathology (No BW: 3235–4050 g. Chen Siyu et al. 2020 25–31y/o, 38 + 4–40 + 4wks’ 0, 1 and 3 days 5 Not tested placental infarction and chorionic NA NA All neonates tested [21] gestation PP amniotic inflammation) -ve Signs of MVM: infarction (n = 7), increased perivillous fibrin SARS-CoV-2 in deposition (n = 4), accelerated villous villous maturation (n = 5), (IHC) +ve SARS-CoV-2 S syncytiotrophobl decidual vasculopathy (n = 2), & N proteins in STs. ast, Hofbauer intervillous thrombosis (n = 4), Monocytes-macrophages cells, fetal subchorial haematoma (n = 1) BW: 1499–4150 g. ** Facchetti et al. 26–44y/o, 32 + 6–41 + 3wks’ All +ve, IHC, TEM (only 1 & neutrophils (CD11c, endothelial 15 Signs of FVM: Chorangiosis (n = One neonate 2020 [22] gestation Unclear when +ve) CD14, CD68, CD163). capillary cells & 4), VSK (n = 1), avascular villi (n = tested +ve Scattered CD3+- intravascular 1). Inflammation: lymphocytes. PD-L1 mononuclear chorioamnionitis (n = 1), villitis (n weak-moderate +ve cells, fibroblasts, = 1), intervillositis (n = 2), acute in maternal deciduitis (n = 2), choriovasculitis macrophages &/ fetal vasculitis (n = 2) No significant pathology (n = 1) Gross: Mild subchorionic fibrin deposition & a single ischaemic area in chorionic disc, slightly 30y/o, G1P0, 38 + 3wks’ hyperspiralised umbilical cord. ** Ferraiolo et al. gestation, asymptomatic. BW: NA 1 +ve PP RT-PCR (+ve) Histo: signs of villous delayed NA NA 2020 [23] Delivered via CS for breech Neonate tested -ve maturation, focal presentation microchorangiosis,moderate fibrin deposition, villous agglutination, intervillous thrombosis Diagnostics 2021, 11, 94 3 of 7 Signs of MVM: infarction (n = 4), distal villous hypoplasia (n = 2), increased perivillous fibrin (n = 6), intervillous thrombosis (n = 13), 24.25–33.75y/o, 38.45–40.1wks’ retroplacental thrombus (n = 2), gestation, with COVID-19 old haemorrhage in membranes (n BW: 2771–3435 g Gulersen et al. 2020 0–20 days prior 50 symptoms: 9 mild, 3 moderate, Not tested = 1), Signs of FVM (n = 4), delayed NA NA All neonates tested [24] delivery 2 severe, 1 critical disease. villous maturation (n = 10), -ve Delivered via 12CS, 38VD chorangiosis (n = 3). Inflammation: chorioamnionitis (n = 9), villitis (n = 2), chorionitis (n = 11), fetal vasculitis (n = 7). Others: meconium (n = 9) Placental weight: 54–797 g Signs of MVM: infarction (n = 2), increased perivillous fibrin deposition (n = 2), decidual (IHC) +ve SARS-CoV-2 vasculopathy (n = 3), intervillous / on ST (n = 2). (ISH) +ve subchorionic thrombosis (n = 4) SARS-CoV-2 on STs, CTs 22–42y/o, 22–41+1wks’ Signs of FVM: Chorangiosis (n = & decidual endothelial BW: NA gestation, 2 sets of twins, 9 days prior 1), VSK (n = 1), avascular villi (n = ** Hecht et al. 2020 IHC & ISH cells (n = 3). One IUD (not 20 7 asymptomatic, 8 mild delivery to 2). Inflammation: NA [25] (3 +ve) +ve ACE2 on STs, CTs tested), One symptoms, 5 severe COVID-19. 1 day PP chorioamnionitis/subchorionitis (n and EVTs. TMPSSR2 neonate tested +ve Delivered via 12CS, 8VD = 7), villitis (n = 1), intervillositis (n weak in villous = 1), chronic deciduitis (n = 2), endothelium & rarely in choriovasculitis / fetal vasculitis (n STs (n = 10) = 4). Others: meconium (n = 5), villous oedema (n = 2), hypercoiling cord (n = 1), marginal insertion of cord (n = 1) Umbilical cord Gross: marginal adherent blood +ve virus tested +ve & clot associated with a focal ** Hosier et al. 2020 +ve on (IHC & ISH) +ve SARS– particles within Neonate tested - 1 35y/o, G3P1, 22wks’ gestation. RT-PCR (+ve) placental infarct. [26] admission CoV-2 S protein in STs the cytosol of ve. Histo: diffuse perivillous fibrin & placental cells Autopsy: histiocytic intervillositis. unremarkable 29y/o, multigravida, 40+4wks’ Gross: marginally inserted (IHC) +ve SARS-CoV-2 N ** Hsu et al. 2020 gestation, with mild COVID-19 2 days prior umbilical cord, 538g (60th protein in chorionic villi BW: 3561g 1 IHC (+ve) NA [27] disease. delivery percentile). Histo: hypertrophic endothelial cells, rarely Neonate tested -ve Delivered via VD arteriolopathy & subchorionic trophoblasts Diagnostics 2021, 11, 94 4 of 7 laminar necrosis, chronic villitis, scattered islands of EVT BW: 2930 g 40y/o, G2P1, 35+5wks’ CD68+ macrophages, ** Kirstman et al. 1 day prior Chronic histiocytic intervillositis Neonate tested 1 gestation. RT-PCR (+ve) CD3+ T cells, CD20+ B NA 2020 [28] delivery & extensive early infarction +ve Delivered by CS cells identified. 30y/o, G2P0+1, monochorionic BW: 2190 g & 2160 diamniotic (MCDA) twin, 2 days prior Accelerated villous maturation & g Kuhrt et al. 2020 [29] 1 (twins) Not tested NA NA 32+6wks’ gestation.Delivered delivery mild hypoperfusion Both neonates by CS tested -ve 38y/o, G6P2, 38+5wks’ SGA placenta (<5%), acute Autopsy: no Lokken et al. 2020 46 (only 1 +ve on RT-PCR IHC for cytomegalovirus gestation. chorioamnionitis, mild funisitis, NA abnormalities [30] examined) admission (-ve) -ve Delivered by VD severe chronic villitis Neonate tested -ve Placenta weight: 526–649 g Signs of MVM: infarction (n = 2), increased perivillous/intervillous fibrin deposition (n = 6), decidual vasculopathy (n = 3), accelerated villous maturation (n = 1), intervillous thrombosis (n = 1) (ISH) +ve SARS CoV-2 BW: 2790–3500 g, Signs of FVM: thrombi in fetal RNA in endothelial cells Umbilical cord 27.6–39.7y/o, 39–40+5wk, with circulation (n = 2), delayed villous 4, 5, 18, 35 days of decidua. blood, breast milk, ** Menter et al. 2020 mild COVID-19 (n = 3), RT-PCR & ISH maturation (n = 1), chorangiosis (n 5 prior delivery (IHC) weak +ve ACE2 in NA amniotic fluid [31] asymptomatic (n = 2). (+ve in one case) = 2). Inflammation: chronic villitis & 1 day PP invasive EVT (n = 4). tested -ve Delivered via 2CS, 3VD, (n = 2), chronic histiocytic CD8+ T cells, CD68+ No data on intervillositis (n = 1), macrophages neonates chorioamnionitis/subchorionitis (n = 3), chronic deciduitis (n = 2), choriovasculitis / fetal vasculitis (n = 3). Others: meconium (n = 1), hypercoiling cord (n = 3), marginal insertion of cord (n = 1), placenta accreta (n = 1) Placenta grossly normal. Histo: increase in perivillous fibrin (>30– 40%) leading to trophoblast (IHC) +ve SARS-CoV-2 in BW: 1920 g (58th ** Mongula et al. 27y/o G2P1 @ 32+1wks’ +ve on 1 RT-PCR (+ve) necrosis, reduced intervillous trophoblasts & stromal NA percentile) 2020 [32] gestation.Delivered via CS admission space possible infarction, cells Neonate tested -ve extensive histiocytic & neutrophilic intervillositis Diagnostics 2021, 11, 94 5 of 7 Signs of FVM: thrombosis in (IHC) -ve SARS-CoV-2 S larger vessels in the fetal protein & (ISH) -ve viral circulation (n = 5), intramural 26–40y/o, 38–40wks’ gestation, RNA in placenta fibrin (n = 4), VSK (n = 1), Mulvey et al.