Is a yolk sac present with a blighted ovum?

Yes , possible: Blighted ovum is when gets implanted with out embryo , detected by sonogram , will have placenta, HCG will be positive , yolk sac may be present with out an embryo , could be due to abnormality chromosomes , one of the common cause of miscarriage

It can be: A blighted ovum means the embryo (the actual baby to be) either does not develop or dies very early in utero. Since the embryo is the last of the early anatomy detected by us (first gestational sac and double decidual sac sign, then yolk sac and finally fetal pole/embryo), the others can be present, and a pregnancy test can be positive, without a fetal pole.