Fetal Ultrasound
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**draft; this topic is currently being authored **
Introduction
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.
Gestational sac seen, no heartbeat
- use beta-hcg to correlate with age
Choroid plexus cyst
- normal development change
- can be a marker for Trisomy 18, but this is extremely rare
Echogenic cardiac focus, hyperechogenic bowel, mild ventriculomegaly are associated with increased risk for Down's.
No nasal bones (21-fold increase) increased nuchal translucency 3.5 (
Low-lying placenta should be re-ordered in 4 weeks if it is within 2cm of the os.
Borderline large kidneys: not concerning.
Unable to clearly visualize heart, kidney, or outflow tract.
Resources and References
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