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In North America placenta praevia occurs in 2.9 per 1000 pregnancies. Ethnic differences indicate white women are less likely to experience placenta praevia than black women. Additionally, more cases of placenta praevia are found in women from low-income areas which are linked to insufficient pregnancy care.
Risk factors include low-lying placenta, in vitro fertilization. [1] Vasa praevia occurs in about 0.6 per 1,000 pregnancies. [1] The term "vasa previa" is derived from the Latin; "vasa" means vessels and "previa" comes from "pre" meaning "before" and "via" meaning "way". In other words, vessels lie before the fetus in the birth canal and in the ...
This can lead to fetal malformations [2] [24] and low birth weight. [ 2 ] [ 6 ] [ 10 ] The umbilical vessels may also be longer compared to normal, [ 2 ] particularly when the site of velamentous cord insertion is in the lower uterine section as the extension of the uterine isthmus as pregnancy advances causes vessel elongation. [ 3 ]
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.
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 ...
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]
Sacrum posterior (SP)—the buttocks face posteriorly. Shoulder presentation with transverse lie are classified into four types, based on the location of the scapula (shoulderblade); note: the presentation is significantly different from asynclitic positioning , and in most cases needs to be delivered by cesarean section .
Placenta can also be divided according to what kind of structure it develops from. There are two vessel-rich features in the amniote, the yolk sac and the allantois. When the chorion fuses with the former, the result is a choriovitelline placenta. When it fuses with the latter, the result is a chorioallantoic placenta.