Is it normal 2 only see a 15mm gestational sac and yolk sac 6.2weeks?

Yolk sac: This may not be normal if you are not off on your dating. It could represent a miscarriage. However, if you are off on dating, you can do another ultrasound and/or have your doctor perform a series of pregnancy tests at least every 48 hours apart. Either or both (preferably) can help give you an answer. Normally, the blood test numbers will go up by 50% in a 48 hr time period.