Pre-vascular causes

Etiology:

Pre-vascular etiology is unknown, the following were the scholars and unsubstantiated assumptions. 1900 Franque think pedicled lower body in normal circumstances (the primordial umbilical cord) and blood always for the most abundant site of contact with human chorionic decidua into the fetus; if at early pregnancy, the blood supply of the richest parts of packets are exuviate pedicle membrane origin of this body, but with the progress of pregnancy, the blood supply of the most abundant in this region has changed at the end of decidua, the placenta in this form, but the body is still in situ pedicle, here villous atrophy has become a smooth chorion, so The site was fan-shaped distribution of blood vessels due to the umbilical cord attached to the edge of the placenta after Strausman (1902) was fan-shaped attachment to the umbilical cord at the beginning of the end of decidual placenta plant in the future, because of placental blood perfusion to the better regional extensional , and attached to the original

Central parts of the umbilical cord so that the edge of eccentricity gradually become attached to, and around the site of placental attachment to the cotyledon degradation become smooth chorion, and finally develop into the umbilical cord after the fan-shaped attachment Benirschke and Driscoll (1967) view is basically the same.

With the pre-vascular risk factors associated with the relationship between the more abnormal placenta, in the placenta previa, placenta futaba, Vice placenta, multiple pregnancy in pre-prone vessel, especially in the twin-fan-shaped attachment of the umbilical cord, about 10%, so easily associated with vascular front. Also report that the pre-vascular malformations in the fetus increased, such as urinary tract malformation, spina bifida, ventricular septal defect, single umbilical artery and so on.

Pathogenesis:

Pathogenesis is unclear. In the course of embryonic development, body pedicle are the primordial umbilical cord. Under normal circumstances, body pedicle and blood supply from the most abundant decidua into contact with the chorionic fetal Franqua (1900) made early pregnancy when the blood supply has probably the most abundant decidua decidua and body kits are pedicle that originated in this. With the progress of pregnancy, the blood supply of the rich moved to the end of decidual zone (the future of placental site), while the body remained in situ pedicle, it becomes smooth chorion chorionic atrophy, resulting in fan-shaped umbilical cord attached to the placenta and umbilical cord blood tube stretching the edge of . In short, the umbilical cord occurred in blastocyst implantation Office across from Benirschke and Driscoll (1967) consider the beginning, the umbilical cord attached to the normal, followed by leaf-like villi to look for a better blood supply to the decidual part of the nutritional intake of more single - to the growth of stretching the umbilical cord is left behind, their attachment Department villus atrophy due to malnutrition, a smooth chorion. The more reasonable argument, could be interpreted two-leaf placental umbilical cord between the fan-shaped attachment; also interpret twin pregnancy, the two close to the implantation of the blastocyst because of turf-related battles happen more often fan-shaped umbilical cord attached. With the umbilical cord attached to the fan-shaped lower uterine segment occurred in the fetus at this presentation before the scattered across the cervical internal carotid vascular mouth, pre-formed blood vessels.