Whats this called on the ultrasound?

[Tattybear2706]

Hi,

When i got to 7/8 weeks with my miscarriage and with this pregnancy (7wks 3daya) inside the gestational sac in addition to the yolk sac was a large thin circle shape, whats this called? Thanks

 

[Tattybear2706]

After much googling apparently its called the amniotic cavity. If anyone is interested here is what I meant https://www.fetalultrasound.com/online/text/4-011.HTM