Placental Abruption
Premature separation of a normally sited placenta: decidual bleeding strips the placenta off the uterine wall, so pain, hypertonus, fetal hypoxia and coagulopathy appear with almost no visible blood.
Definition
Placental abruption is premature separation of a normally sited placenta before birth, from 24+0 weeks of pregnancy onwards. Bleeding may be revealed at the introitus, wholly concealed behind the placenta or within the myometrium, or both. It is a clinical diagnosis: there is no sensitive or reliable diagnostic test.
First principles
Abruption is a clinical diagnosis and the scan usually misses it
Ultrasound has a sensitivity of only 24% for retroplacental clot, so it fails to detect three-quarters of abruptions. Specificity is 96%, so a positive scan is close to diagnostic. Scan to establish placental site and to confirm fetal heart activity, never to rule abruption out.
This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.

