Reliability of placental histology using archived specimens

Archived placental materials provide a resource for retrospective studies of perinatal outcomes. Using archived specimens, we evaluated inter-rater reliability in the assessment of placental histological features possibly associated with neonatal illness and long-term neurological outcome. Five expert placental pathologists independently reviewed archived placental specimens on 30 subjects born during 1983-85 in six different hospitals. Moderate to substantial agreement among the raters was observed for a variety of indicators of inflammation, presence of macrophages with pigment and indicators of villous maturity, increased syncytial knots and maternal vasculopathy. Existing pathology reports for these specimens from routine histology examinations conducted at the time of delivery were in substantial agreement with expert review for the presence of any subchorionitis/chorionitis/chorioamnionitis. In conclusion, considerable inter-rater agreement was observed for several relatively common and potentially important placental findings. Archived placental materials and pathology reports may be useful in retrospective studies.