What Causes An Absence Of The Fetal Pole?

hello doc , i am pallavi from india,i am 34 years old and been married 3 yrs back, i conceived after 2 months of marriage but as there was no foetal pole found my doc aborted it, after 2 years there was another abortion in very early stages of pregnancy that was just 4 weeks ,now i am pregnant again, and i am in my 6th week now, i just a scan done and there was a G.sac of 8.9mm size and my doc said it was only 4 weeks and asked to come for a rescan after 2 weeks,



i want to know what are reason for absence of foetal pole even after formation of gestational sac