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Placenta previa is itself a risk factor of placenta accreta. Alcohol use during pregnancy was previously listed as a risk factor, but is discredited by this article ...
Placenta previa is a condition that occurs when the placenta fully or partially covers the cervix. [13] Placenta previa can be further categorized into complete previa, partial previa, marginal previa, and low-lying placenta, depending on the degree to which the placenta covers the internal cervical os.
The placenta grows in regions with better blood supply and portions atrophy in regions of poor blood flow. This process of atrophy may result in the exposure of umbilical blood vessels, causing marginal or peripheral placental insertion to evolve to velamentous insertion over time.
An important risk factor for placenta accreta is placenta previa in the presence of a uterine scar. Placenta previa is an independent risk factor for placenta accreta. Additional reported risk factors for placenta accreta include maternal age and multiparity, other prior uterine surgery, prior uterine curettage, uterine irradiation, endometrial ablation, Asherman syndrome, uterine leiomyomata ...
A placental infarction results from the interruption of blood supply to a part of the placenta, causing its cells to die.. Small placental infarcts, especially at the edge of the placental disc, are considered to be normal at term.
Besides placenta previa and placental abruption, uterine rupture can occur, which is a very serious condition leading to internal or external bleeding. Bleeding from the fetus is rare, but may occur with two conditions called vasa previa and velamentous umbilical cord insertion where the fetal blood vessels lie near the placental insertion site unprotected by Wharton's jelly of the cord. [11]
Along with placenta previa and uterine rupture it is one of the most common causes of vaginal bleeding in the later part of pregnancy. [6] Placental abruption is the reason for about 15% of infant deaths around the time of birth. [2] The condition was described at least as early as 1664. [7]
In a circumvallate placenta, the membranes often become restrained due to marginal infarct, hemorrhage, or fibrin depositing. This results in the reduction in size of the chorionic plate of the placenta , further causing the membranes on the fetal side to fold backward on themselves.