This is essentially a pregnancy of uncertain viability (PUV), and should be followed up to establish fetal viability. However the large yolk (8mm where n<6mm) is a poor prognostic factor, increasing the likelihood that this pregnancy will not progress.
There is also some evidence which suggests increased risk of abnormal karyotype in viable gestations where there was an initial finding of an enlarged yolk sac1. At the time of writing, there is no defined guideline regarding follow-up of such pregnancies.