MRI Evaluation of Post-COVID Placentitis: A Rare but Devastating Cause of Fetal Demise

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 MRI Evaluation of Post-COVID Placentitis: A Rare but Devastating Cause of Fetal Demise

DOI:10.1259/bjrcr.20220132

Introduction

Since the emergence of the SARS-CoV-2 virus, a growing number of studies have reported adverse pregnancy outcomes linked to COVID-19. Among the most alarming is post-COVID placentitis, a pathological condition in which the placenta exhibits widespread fibrin deposition and inflammation following maternal infection. Although relatively rare, this condition can lead to intrauterine growth restriction (IUGR) and stillbirth, often without any significant maternal symptoms.

This article presents a detailed case of post-COVID placentitis diagnosed via antenatal MRI, and discusses its radiologic, clinical, and histopathologic features. We explore how advanced imaging techniques such as diffusion-weighted imaging (DWI) and T2-weighted MRI can aid in early diagnosis and timely intervention. This post is written with SEO-rich keywords to help elevate visibility and inform clinicians, radiologists, and researchers.

Case Summary: MRI of COVID-19 Affected Placenta

A 30-year-old woman, gravida 2 para 1, with a prior normal delivery and a normal fetal anomaly scan at 22 weeks of gestational age (GA), contracted COVID-19 at 24 weeks. She recovered without complications but noted reduced fetal movement at 27 weeks. Ultrasound revealed bright echoes in the fetal brain, small lungs, and oligohydramnios, prompting an MRI evaluation.

Figure 1. Sagittal diffusion-weighted MRI image showing markedly reduced placental signal intensity.


MRI Findings

The MRI revealed the following abnormalities:

  • Abnormal brain signal intensity

  • Oligohydramnios

  • Small lungs

  • Extremely abnormal placenta, characterized by:

    • Reduced and heterogeneous T2-weighted signal

    • Marked reduction in DWI signal intensity

    • Small placental volume (14% of expected size)

    • Surface area of attachment is also 14% of the expected for GA

Figure 2.  Macroscopic placental surface showing marbling effect due to massive perivillous fibrin deposition (A, B); H&E staining showing fibrin (C); Brain section with calcified neurons (D).


Diagnosis: Post-COVID Placentitis

Based on the clinical history, MRI findings, and histopathology, a diagnosis of post-COVID placentitis was made. Immunohistochemistry confirmed SARS-CoV-2 positivity in the syncytiotrophoblast, providing conclusive evidence of placental infection.

Clinical Course and Management

Despite the lack of a definitive diagnosis at 27 weeks, fetal echocardiography and close monitoring were recommended. However, the parents opted for termination of pregnancy at 30 weeks and 2 days due to poor fetal prognosis. A stillborn male weighing 780 g was delivered (significantly below the normal weight of 1115 ± 329 g for GA).

Pathology Report

  • Fetal autopsy showed hypoxic changes and neuronal calcification.

  • The placenta was markedly small and exhibited massive perivillous fibrin deposition.

  • Histology confirmed chronic deciduitis, a hallmark of placental inflammation.

  • Immunostaining confirmed SARS-CoV-2 in the syncytiotrophoblast.

Pathophysiology of Post-COVID Placentitis

COVID-19-related placental damage is now a recognized pathological entity. The exact mechanism remains under investigation, but the proposed process includes:

  • Endothelial injury

  • Hypercoagulability

  • Maternal immune response

  • Viral invasion of syncytiotrophoblast via ACE2 receptors

Massive perivillous fibrin deposition (MPVFD) impairs maternal-fetal exchange, resulting in placental insufficiency, hypoxia, and ultimately fetal demise.

Role of MRI in Diagnosis

MRI offers a superior modality over ultrasound in detecting placental abnormalities, especially when Doppler is non-diagnostic.

Key MRI Features:

  • T2-weighted images: Heterogeneous hypointensity due to fibrin deposition

  • DWI: Reduced signal intensity (contrasts with previously reported increased DWI in demised fetuses)

  • Small placental volume and reduced attachment area

These features can predict placental insufficiency before irreversible fetal damage occurs.

Epidemiology and Risk Factors

Though rare, post-COVID placentitis has been increasingly reported during waves dominated by specific virus variants:

  • Alpha (B.1.1.7) and Delta (B.1.617.2) variants have been associated with the majority of stillbirths linked to COVID-19.

  • IUGR and fetal death may occur even after mild maternal illness, underscoring the unpredictable severity of placental involvement.

Implications for Clinical Practice

When to Suspect Post-COVID Placentitis:

  • History of COVID-19 during pregnancy

  • Reduced fetal movements

  • IUGR with otherwise normal fetal anatomy

  • Abnormal placental signal on MRI

Recommended Actions:

  • Prompt MRI evaluation

  • Fetal echocardiography

  • Twice-weekly ultrasound for growth and Doppler studies

  • Early delivery planning if placental compromise is suspected

Quiz

1. What is the most characteristic diffusion-weighted MRI (DWI) feature of the placenta in post-COVID placentitis?

(1) Normal signal intensity

(2) Increased signal intensity

(3) Reduced signal intensity

(4) Not possible to assess

2. Which of the following histopathological findings is most characteristic of post-COVID placentitis?

(1) Chorioamnionitis

(2) Villitis of unknown etiology (VUE)

(3) Massive perivillous fibrin deposition

(4) Subchorionic hematoma


3. Which MRI feature most strongly supports a diagnosis of post-COVID placentitis?

(1) Increased T2-weighted signal with homogeneous placental texture

(2) Enlarged placental volume with normal DWI signal

(3) Heterogeneous T2-weighted signal and markedly reduced DWI signal

(4) Normal T1 and T2 signal with adequate placental size

Answer & Explanation

1. Answer:(3) Reduced signal intensity. Explanation: Unlike some previous reports that showed increased DWI signal post-demise, this case demonstrated markedly reduced DWI signal intensity, indicating perivillous fibrin deposition and hypoperfusion, confirming placental insufficiency.

2. Answer: (3) Massive perivillous fibrin deposition. Explanation: Post-COVID placentitis is pathologically defined by massive perivillous fibrin deposition, often with associated chronic deciduitis and positive immunostaining for SARS-CoV-2 in the syncytiotrophoblast. This finding distinguishes it from other causes of placental inflammation, such as chorioamnionitis or VUE.

3. Answer:(3) Heterogeneous T2-weighted signal and markedly reduced DWI signal.  Explanation: Post-COVID placentitis typically presents with heterogeneous low signal intensity on T2-weighted images due to massive perivillous fibrin deposition, and a markedly reduced signal on DWI, reflecting impaired perfusion and hypoxic damage. These imaging findings are critical to distinguishing this condition from other causes of IUGR or placental insufficiency.

References

[1] R. Hecht et al., “SARS-CoV-2 placentitis and intrauterine growth restriction: Imaging and histologic correlation,” AJR Am J Roentgenol, vol. 218, no. 5, pp. 975–982, May 2022.

[2] M. Shanes et al., “Placental histopathology in COVID-19,” Am J Clin Pathol, vol. 154, no. 1, pp. 23–32, Jul. 2020.

[3] E. Schwartz et al., “Stillbirth during COVID-19 pandemic: Possible placental involvement,” Am J Obstet Gynecol, vol. 224, no. 1, pp. 15–23, Jan. 2021.

[4] C. Patberg et al., “Placental pathology in COVID-19 positive pregnancies,” Am J Obstet Gynecol MFM, vol. 2, no. 3, p. 100211, 2020.

[5] Centers for Disease Control and Prevention (CDC), “Pregnancy and COVID-19 outcomes,” Nov. 2021. [Online]. Available: https://www.cdc.gov

[6] Royal College of Physicians of Ireland, “COVID-19 and pregnancy statement,” Jan. 2022. [Online]. Available: https://www.rcpi.ie

[7] M. Argueta et al., “Placental histopathology in SARS-CoV-2 infection,” Placenta, vol. 103, pp. 80–88, Dec. 2021.

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