Fetal biometry. The common tomograms used : Axial Coronal Sagittal (midline). F etal biometry . Fetal growth can be monitored accurately later in life only if the exact information about the GA is available. As less than 50% of women are certain about their LMP.
Gestational age: length of the pregnancy based upon reliable LMP, assuming that conception occurs 14 days later.
Several US parameters have been used to estimate GA, the most commonly used are:
Mean sac diameter
Gestational sac volume
Crown rump length
After 12wa CRL m inaccuracy of 7-10days
The end point of the crown & rump clearly defined
Placing the calipers correctly on this defined end point.
This is not to be recommended under any circumstances
How easy to produce errors of 10-15mm simply by
measuring 12-13ws fetus incorrectly
–assessing gestational age
Lateral ventricles view
A rugby- football- shaped skull, rounded at the back (occiput) and more pointed at the front (synciput).
Short midline equidistant from the proximal and distal skull
It’s a beast dater of pregnancy.
TCD in mm= ws of gestation
A circular section of the abdomen ,unbroken & short rib echo of = size on each side.
B. This is the correct level for AC.
C. this plane is too inclined in a craniocaudal axis.
Dolichocephaly ( narrow BPD) ,75
Brachycephaly (wide BPD)
Lumbar spine, transverse axial sonogram, 23 weeks. Well-defined ossification of the laminae (L). C, centrum; arrows, neurocentralsynchondroses.
Observe the fetal abdomen in both cross & longitudinal section to exclude evidence of obstruction or area of increased echogenicity:
Echogenic foci of the liver
When the planter or foot print obtained with the same section with tibia & tibia talipes should be suspected.