The relationship among timing and severity of COVID-19 during pregnancy, placental pathology, and adverse pregnancy outcomes is not well understood. We conducted a prospective cohort study of 497 pregnant patients with COVID-19 whose placentas underwent systematic pathologic examination. The main exposure was timing of COVID-19 during pregnancy (first or second versus third trimester). The primary outcome was composite placental pathology that included high grade maternal vascular malperfusion or greater than 25 percent perivillous fibrin deposition. There were 63 patients who had the composite placental pathology outcome. In adjusted analyses that controlled for maternal age, parity, active infection at delivery, interval from time of diagnosis to delivery and COVID-19 variant, timing of COVID-19 during pregnancy was not associated with risk of the composite placental pathology outcome. Among secondary COVID-19 related exposures we investigated, severity of disease and treatment for COVID-19 were associated with risk of the composite placental pathology outcome. In addition, patients with COVID-19 in the first nine months of the pandemic had the highest rate of the composite placental pathology outcome. In this large cohort, placental vascular pathology was common among COVID-19 cases but was unrelated to timing of COVID-19 during pregnancy or adverse pregnancy outcomes. These findings suggest that uncomplicated COVID-19 during pregnancy does not require intensive fetal surveillance or detailed pathologic examination of the placenta after delivery.

The authors have declared no competing interest.

March of Dimes- COVID-19 grant, ES019851, and ES013508

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This study was carried out with Institutional Review Board approval (protocol #843277) from the University of Pennsylvania (HUP), Philadelphia, PA

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