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Amniotic shelf

Dr Yuranga Weerakkody et al.

An amniotic shelf (also known as an amniotic sheet ⁴) refers to a sheet like projection that can result from uterine synechiae that has been encompassed by the expanding chorion and amnion. In contrast to amniotic bands, they are not thought to be associated with any fetal deformity.

Epidemiology

The estimated prevalence is at around 0.45-0.47 % of pregnancies ⁵.

Pathology

They are composed of four distinct layers : two layers of chorion sandwiched between two layers of amnion.

Radiographic features

Antenatal ultrasound

They may be are seen as 'shelves' in the amniotic cavity.

Complications

They can be result in abnormal fetal presentations (e.g breech presentation) by reducing fetal movement by compartmentalising amniotic fluid ⁵.

Prognosis

Most amniotic sheets are considered benign (especially if they are incomplete ²). But there is some evidence that complete amniotic sheets may be associated with adverse fetal outcome ². Some authors suggest that perpendicular, in contrast to non-perpendicular, amniotic sheets are more commonly associated with a breech presentation at term ³.