178 Obstetrics and Gynecology Board Review •••
❍ What NT is greater than the 99th percentile throughout the measured gestational ages?
3.5 mm.
❍ While performing NT, what structure shown below may be a useful marker for detection of aneuploidy?
Nasal bone.❍ What technique should be utilized for nasal bone (NB) measurements?
- Fetus magnified so that only the head and upper thorax are in the screen.
- Precise midsagittal view of the fetal profile.
- Fetal spine down with slight neck flexion.
- Transducer parallel to the direction of the fetal nose (45–135 degrees).
- Three distinct lines should be seen.
❍ What is the ductus venosus?
A trumpet-shaped vein connecting the umbilical sinus to the hepatic veins and the IVC, directing high velocity
oxygenated blood returning from the placenta to the left atrium via the foramen ovale.
❍ What is the normal Doppler waveform pattern in the ductus venosus?
Biphasic pulsatile continuously forward flow.
❍ What heart abnormalities may be apparent in the first trimester, but may be resolved by the third trimester?
Muscular ventricular septal defect.