Is Oval Gestational Sac Abnormal During Pregnancy?

wife is 6 weeks 2 days and first ultrasound today. heartbeat 122 and size accordingly, but sac is not circular in shape, it s more ovular and a little irregular on one end. we had a miscarriage last fall and fear the same will happen with this baby. next US in a week, but i m looking for (reassuring) info to help my wife not go crazy this next week. thank you