The gestational sac contains amniotic fluid and surrounds the embryo. You may see the gestational sac in an ultrasound as early as 4 1/2 to 5 weeks.The gestational sac

How many weeks can scan detect pregnancy?

In viable pregnancies, trans-vaginal (internal) scans should be able to detect a gestation sac from 5 weeks of pregnancy. A yolk sac can be seen at 5 1/2 weeks gestation. Trans-abdominal (external) scan may be less accurate at this early 5 week stage.

What can I expect to see on a 4 week ultrasound?

4 Week Ultrasound Some cells will become part of the placenta. Some will form the amniotic sac that will fill with fluid to cushion your developing baby. Other cells are destined to form everything from delicate eyelashes to muscles and skin. But thats still a long way away.