My Wife Has Last Period 10th September.confirmed Pregnancy On 15th

My wife has last period 10th September.confirmed pregnancy on 15th October.went for first scan on 6w 3days and confirmed pregnancy.went for second scan on 7w 6days.doctor said gestational sac is small.given system and other supplements.asked to come again after 10 days to sew the growth.when asked abt heart beat. She said hear beat is there but just started..do we have possibility of sac to grow.how much hope ia there?