Etiology
The precise etiology of abruption is unknown. However, abruption may result from a variety of different pathways.
Direct abdominal trauma may cause separation of the placenta.
Indirect trauma may shear the placenta off the uterine wall.
Cocaine use causes vasospasm that may lead to placental separation.
Pathology exams of placentas that have undergone abruption frequently show evidence of chronic inflammation, suggesting that abruption is often the end result of a long-standing chronic process.[7] Conversely, acute events such as cocaine use, or trauma, particularly from motor vehicle accidents, may lead to abruption in an otherwise entirely normal pregnancy. It has been observed that abnormal uterine artery Doppler velocimetry at 23 to 24 weeks' gestation may carry an increased risk of abruption later in pregnancy, supporting the concept of a long-standing process in some women.[8][9]
A study of placental bed biopsies of women who have had abruptions found a lack of trophoblastic invasion, a lesion similar to that found in preeclampsia, in three-fifths of these women.[10] Women who have preeclampsia, abruption, or intrauterine growth restriction have an increased risk of developing any of these complications in a subsequent pregnancy.[11] Indeed, all three conditions have been found to be associated with thrombophilias, conditions with an increased propensity for abnormal coagulation within the placenta.[12] This has led to the concept that a significant proportion of these three conditions, particularly if seen in preterm gestations, belong to a spectrum of ischemic placental disease and share a common etiology.[11][12] However, the American College of Obstetricians and Gynecologists guideline recommends that thrombophilias are no longer tested for after placental abruption, as they do not appear to increase the risk of abruption.[13]
Pathophysiology
Pathophysiology remains unknown.
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