biometric measurements are defined as follows:
Crown-Rump Length (CRL):
This measurement is
obtained from fetuses between 9 to 14 weeks. The measurement is performed considering the outer borders of the head
2. Biparietal diameter (BPD):
should be taken on the outer border of the parietal bones (‘outer to outer’) at
the widest part of the skull.
3. Occipito-Frontal Diameter (OFD):
should be taken on the outer border of the occipital and frontal edges of the
skull at the point of the midline (‘outer to outer’) across the longest part of
4. Head circumference (HC):
will be calculated from the BPD and OFD measurements using the formula HC = π(BPD +
5. Antero-posterior abdominal diameter (APAD):
measurement is taken on the outer borders of the body outline from the
posterior aspect (skin covering the spine) to the anterior abdominal wall.
6. Transverse abdominal diameter (TAD):
measurement is taken on the outer borders of the body outline at 90° to the
APAD, across the abdomen at the widest point.
7. Abdominal circumference (AC):
will be calculated from the APAD and TAD measurements using the formula AC = π(APAD +
8. Femur length (FL):
is taken on the outer borders of the edges of the femoral bone ‘outer to outer’.
The trochanter is not to be measured.