Thrombosis of fetal placental vessels. A quantitative study in placentas of stillbirths.

Microscopical examination of 50 placentas of stillborn infants and 50 of normal infants (controls) was performed for detection of thrombosis in the stem fetal vessels. Fresh fibrin thrombi occurred with equal frequency in stillborns and normal infants, suggesting that these thrombi are not necessarily of pathological significance. In normal infants they might be related to clamping of the umbilical cord. In placentas of normal infants and of stillbirths with 1 day of placental retention (P.R.) organizing thrombi were rare and when occlusive they were related to avascular villi, which suggests that they were pre-mortem in origin. By contrast organizing thrombi were found in 78.5% of placentas of stillbirths with 2-7 days of P.R, where arterial occlusive thrombi were rarely associated with avascular villi. With over 7 days of P.R. they were almost fully organized. These findings suggest that most organizing thrombi in placental vessels of macerated stillbirths are probably post-mortem clots in process of organization by the still living placenta and should therefore not be attached pathological significance.