Twin transfusion: pathological studies of the monochorionic placenta in liveborn twins and of the perinatal autopsy in monochorionic twin pairs.

Vascular injections of 21 monochorionic placentas from liveborn twins were scored for chorionic surface vessel anastomoses and for venous return areas. The results were correlated with neonatal birth weight and first hematocrit. Weight and hematocrit differences did not correlate with each other or with placental anastomoses. There was a relationship between weight and placental area to the individual twin. In some cases, weight differences between monochorionic twins may be the result of placental differences rather than chronic transfusion. Seventeen perinatal autopsies of monochorionic twin pairs were reviewed for plethora/pallor and for organ and body weights. Cardiac hypertrophy was present in three autopsies. Cardiac hypertrophy may be a measure of chronic twin transfusion in the recipient. The lighter twin was as likely to be plethoric as the heavier. Plethora postmortem is a poor measure of chronic transfusion because of confounding factors, particularly acute twin transfusion. As a result of these studies, placental anatomy is speculated to be complexly rather than directly related to clinical outcome.