Differences in Placental Pathologic Features by Trimester of Infection with SARS-CoV-2

Introduction: We describe placental findings associated with SARS-CoV-2 infection in pregnancy and any differences between trimester of infection. Methods: We included 314 pregnant patients who tested positive for SARS-CoV-2 during pregnancy and had their placenta submitted for pathology examination. Trimester of infection was based on the gestational age at the time of infection. Placental pathology was categorized into acute inflammation (AI), chronic inflammation (CI), maternal vascular malperfusion (MVM), fetal vascular malperfusion (FVM), and divided into none, low-grade, and high-grade. RT-PCR for SARS-CoV-2 was performed on placenta tissue in 238/314 (75%) cases. Results: The prevalence of AI, CI, FVM, and MVM did not differ by trimester of infection. However, high-grade inflammatory and/or vascular pathology were more prevalent with earlier infection in pregnancy (1st trimester (27/40, 67.5%), 2nd trimester (37/67, 55.2%), and 3rd trimester (82/207, 39.6%, P < .01). Third trimester infection <= 10 days before delivery was associated with a higher prevalence of FVM compared to infection more remote from delivery (46/134, 34.3% vs 14/73, 19.2%; P < .02). We detected SARS-CoV-2 RNA in placenta, in 8/238 (3.4%) of cases. Conclusion: High-grade inflammatory and/or vascular placental pathology are more prevalent with earlier SARS-CoV-2 infection in pregnancy.