Pathological significance of first-trimester fetal nuchal oedema

The pathological mechanism that causes the transient phenomenon sonographically defined as "nuchal translucency' is still poorly understood. Seven pregnancies in which the fetuses clearly presented this ultrasonic sign at 10-14 weeks' gestation were terminated because of an abnormal fetal karyotype. The pathological specimens, compared by morphometric analysis with normal fetuses of the same gestational age, showed oedema and dilatation of lymphatic capillary vessels. No particular relationship was found with any structural abnormality. We speculate that nuchal oedema is a transient non-specific phenomenon which is probably related to an early disarrangement of lymphatic connections.