First-trimester miscarriage: A histopathological classification proposal.

Background: Histopathology of first-trimester abortion products may be useful in document an intrauterine pregnancy, identifying an important pathology affecting the mother or the embryo and diagnosing conditions that are likely to recur in future pregnancies or that explain the adverse fetal outcome. Relevant information provided by histology is essential to determine the cause and to guide the patients with early pregnancy failure.

Aims: Histopathological classification proposal in first-trimester miscarriage.

Methods: Published pathological criteria in first-trimester abortion specimens were collected, standardized and focused into a comprehensive diagnosis. The idea was to create a comprehensive classification related to major pathophysiological processes. Thus, the histological criteria were grouped into 7 categories: i. Changes suggesting aneuploidy (CSA) or metabolic storage disease; ii. Embryo anomaly (EA); iii. Multifactorial (MF) causes; iv. Maternal causes (MC); v. Gestational trophoblastic disease, such as hydatidiform mole (HM) and non neoplastic lesions and neoplasms; vi. Ectopic pregnancy; vii. Other. So, a 6-years retrospective study of first-trimester spontaneous miscarriage were reviewed. Two groups were created: i. Study group include specimens with pathological diagnosis; ii. Control group incorporate specimens with pathological diagnosis and additional genetic study in order to validate pathological criteria.

Results: Pathological criteria concordance between inter-observers was generally good, with an excellent correlation in EA and HM categories. Despite greater inter-observer disagreement in the CSA and MC categories the correlation with the genetic results was very positive.

Conclusion: A standardized, reproducible and biologically comprehensive histopathological classification may improve fetal follow-up and couple's management.