Should I Expect A Miscarriage, Or Can This Still Result In A Viable Pregnancy At 7 Weeks Pregnant With An Enlarged Yolk Sac And No Visible Embryo?

Hi there, I am around 7 weeks pregnant (although dates could be off due to irregular cycle). LMP was 25th February, cycle is normally 21-24 days but was 30 days from January to February. I am 37 years old and this is my first pregnancy. I had an early scan on 9 April, which showed a gestational sac, and an enlarged yolk sac (5.6mm), and no visible embryo (no heartbeat could be heard either). I have had no bleeding, my PTs are still positive and I still have pregnancy symptoms (nausea, breast tenderness, tiredness, bloated). I am now expecting a miscarriage since the sonographer said they would be surprised if my pregnancy turned out to be viable. I will rescan on 25 April (assuming I haven t already miscarried by this date) but just really want to understand if I should assume that a miscarriage is imminent and prepare for it (or if there have been similar cases where the pregnancy later turned out to be viable and led to a healthy baby). Thanks