Biochemical diagnosis of placental infarction/damage: acutely rising alkaline phosphatase

Abstract

There are currently no simple tests in clinical use to detect acute placental damage. A case is described to demonstrate that a routinely used measurement such as alkaline phosphatase (ALP) can be employed to detect acute damage to the placenta. Seventeen serial blood samples, three pre-delivery, were collected from a 22-year-old primigravida who delivered a stillborn baby. Retrospectively, blood samples were analysed for total and heat-stable ALP as well as human chorionic gonadotropin (hCG) and alpha-fetoprotein (AFP) as a measure of placental function when an unusual pattern of change in ALP was noticed. Histological examination of the placenta revealed new and old placental infarcts. Total and heat-stable ALPs as well as AFP peaked by more than eight-, 19- and two-fold, respectively over 16 h. Plasma hCG fell sharply even before delivery of placenta by five-fold over 16 h before further falling slowly to baseline. The fall in hCG is also consistent with the placental damage being acute and critical. As far as we are aware this is the first description of changes in circulating proteins reflecting placental damage.