Fetal Ultrasounds

A transabdominal ultrasound will show a normal pregnancy at 6-8 weeks, while a transvaginal ultrasound will show a gestational sac at 5 weeks and the fetal pole at 6 weeks.

 

The dating ultrasound is best done 8-12 weeks gestational age. Measuring the crown-rump length gives a margin of error +/- 3 days. Fetal growth ultrasounds done at 18-20 weeks have a margin of error +/- 7 days.

 

Nucal translucency ultrasound (NTUS) is done at 11-14 weeks GA to measure the amount of fluid behind the neck. It is an early screen for serious genetic problems such as Down syndrome.