Acute thymic involution in unexplained third trimester stillbirth: frequency, grade, and correlation with...

Area of Science:

• Pathology
• Fetal Medicine
• Neuropathology

Background:

• Many third-trimester stillbirths remain unexplained, with limited understanding of illness duration.
• Histologic acute thymic involution (ATI) correlates with acute illness duration.
• Brain injury is a common finding in stillbirth.

Purpose of the Study:

• To investigate ATI in unexplained third-trimester stillbirths.
• To correlate ATI with neuropathologic injury (gray matter injury and white matter injury).
• To examine relationships between ATI and thymic weight, gestational age, and clinical data.

Main Methods:

• Autopsy data from 58 unexplained, third-trimester stillborns with brain examination were analyzed.
• Acute thymic involution (ATI) was graded from 0 (no change) to 4 (pronounced lymphodepletion).
• Gray matter injury (GMI) and white matter injury (WMI) were classified as older, recent, or absent.

Main Results:

• 84% of stillborns exhibited ATI grades 2-4, suggesting acute illness onset 24-72 hours before death.
• Higher ATI grades significantly correlated with older GMI (P < 0.001) and WMI (P = 0.014).
• Small-for-gestational age stillborns had higher ATI grades (P = 0.017).

Conclusions:

• The correlation between ATI and older brain injury suggests a similar timing of onset and shared pathophysiology in unexplained stillbirth.
• The specific underlying pathophysiologic events require further investigation.
• ATI grading provides insights into the timing of acute illness preceding stillbirth.