| Incidence |
Rare, more common among spontaneous abortions
|
1: 7, 000 - 42, 000, more common in monozygotic twins
|
| Genetic defect |
Unknown
|
Unknown
|
| Pathogenesis |
Rupture of amnion, entrapment of fetal structures by sticky mesodermic bands that originate from the chorionic side of amnion |
1) Amnion rupture
2) Vascular disruption
3) Embryonic malformation
4) Primary malformation of the body wall closure with it's fusion with the amnion during the 1st month of development |
| Clinical features |
Early entrapment (18-24 days post conception): severe craniofacial and internal malformation
Late entrapment: simple amputation or limb defects
Severe cases difficult to distinguish from body stalk anomalies
|
2 distinct phenotypes:
Craniofacial defect, amniotic bands (likely due to early vascular disruption)
Abdominal wall defects, urogenital anomalies, anal atresia, spinal and limb defects, abdomino-placental attachment, short or absent umbilical cord (due to embryologic maldevelopment). |