Thymic pathology in placental abruption: an autopsy study of third trimester stillborns in a predominantly African-American population.

OBJECTIVE

Complete placental abruption results rapidly in fetal death through acute asphyxia, and identification of thymic lesions at autopsy may help in confirming this diagnosis. Thymic petechiae are a marker for acute asphyxia, while absence of histologically identifiable acute thymic involution (ATI), which requires several hours to develop, may help in exclusion.

METHODS

We identified autopsies on 17 3rd trimester stillborns with clinical abruption; 58 stillborns with unexplained demise comprised the control group. Eighty-nine percent of the mothers were African-American. ATI was graded 0-4 (grades 0-1 and 3-4 were combined for analysis), and thymic petechiae were recorded.

RESULTS

In the abruption group, ATI grade 0-1 was more frequent than higher grades: 13 (77%) had ATI grade 0-1 compared to 1 (6%) with ATI grade 3-4 (p < 0.001). In contrast, in the control group, ATI grade 3-4 was more frequent than lower grades: 9 (16%) had ATI grade 0-1 compared to 30 (52%) with ATI grade 3-4 (p < 0.001). Thymic petechiae were more frequent in the abruption compared to control group [10 (59%) versus 2 (3%)] (p < 0.001), and were frequently seen with low ATI grade: 10 (83%) had ATI grade 0-1 (p < 0.001).

CONCLUSIONS

The presence of thymic petechiae and ATI grade 0-1 correlates significantly with a clinical diagnosis of placental abruption.