Placental protein 5: disappearance from the circulation after delivery

Blood was collected from 8 women following delivery at term. The decline in serum concentrations of placental protein 5 following the delivery of the infant's head was studied for 12 h. Placental protein 5 levels fell very rapidly with a half-life of 5-39 min. In the majority of women placental protein 5 was undetectable after 12 h (i.e. less than 2 microgram/l).