amniotic band syndrome

AMNIOTIC BAND SYNDROME (ABS)

 

The amniotic band syndrome is a group of sporadic congenital anomalies characterized by amputations, constriction bands, pseudosyndactylism and multiple craniofacial, visceral and body wall defects. It occurs in 1 in 1200 to 1 in 15 000 live births (1). Although the exact cause of the syndrome is not known, early rupture of the amniotic membrane resulting in bands that insert on the body of the fetus is the most accepted view (1).

 

Sonographic appearance of membrane	Relationship to Fetus
* Thin aberrant bands of tissue attached to the fetus. * Fetal deformities. * Restriction of fetal movement secondary to entrapment by bands. * Bands may be very difficult to visualize    but characteristic fetal deformities in a     non-embryonic distribution is highly suggestive.	* Commonly associated with fetal deformities. * Limb defects.   - Lymphedema (due to constriction ring   - Amputation (asymmetric).   - Distal syndactyly (differentiates ABS from genetic or teratogenic causes).   - Clubbed feet. * Craniofacial defects.   - Lateral meningocele & Encephalocele   - Asymmetric micropthalmia   - Anencephaly / Facial Clefting. * Visceral defects.   - Gastroschisis ± liver exteriorization   - Omphalocele.   - Ectopia cordis.   - Limb-body wall complex.
Relationship to Placenta	Timing	Pathology/Etiology
* Usually none. * Occasionally may constrict the base of the cord at the placental attachment (lethal).	* Early amnion rupture is thought to result in ABS due to the adhesive nature of the external amnion and chorion.	* Entrapment of fetal parts is the result of rupture of the amnion and development of fibrous mesodermal bands on the chorionic side of the amnion. * Recurrence risk is negligible(sporadic)