Gray-scale and color Doppler US findings of amniotic sheets

To identify the gray-scale and color Doppler ultrasonography (US) findings of amniotic sheets.

Among 1201 pregnant patients who underwent detailed second trimester US, nine had amniotic sheets. An amniotic sheet was defined as a shelf-like structure in the uterine cavity with a free edge not attached to the fetus or umbilical cord. There was no major fetal anomaly observed in any patient. Eight patients had solitary amniotic sheets, and one patient had double sheets. All gray-scale and Doppler US features of amniotic sheets were noted.

The incidence of an amniotic sheet was determined to be 0.75% (ten amniotic sheets were observed in nine patients). On gray-scale US images, amniotic sheets were observed as bands of tissue that originated from the uterine wall with a triangular-shaped base that tapered toward the free edge. A three-layered appearance was identified in seven amniotic sheets. Using Doppler US images, four of ten sheets showed a low-resistance arterial flow, and five of ten sheets showed non-pulsatile venous flows. No vascularization was observed in one patient with a thin, membranous sheet.

Gray-scale US is sufficient for the diagnosis of amniotic sheets because of the typical US characteristics; however, Doppler US findings of amniotic sheets are highly variable. Thus, Doppler US may not be beneficial in the diagnosis of amniotic sheets.