Head circumference

Last revised by Dr Jeremy Jones ◉ on 20 Sep 2021

Citation, DOI and article data

Citation:

Stanislavsky, A., Jones, J. Head circumference. Reference article, Radiopaedia.org. (accessed on 09 Dec 2021) https://doi.org/10.53347/rID-26430

DOI:

https://doi.org/10.53347/rID-26430

Permalink:

https://radiopaedia.org/articles/26430

rID:

26430

Article created:

21 Dec 2013 by Dr Alexandra Stanislavsky ◉

Revisions:

17 times by 5 users - see full revision history

System:

Obstetrics

Section:

Tag:

cases, ultrasound, fetal head, second trimester

Synonyms:

Head circumference (HC)

Head circumference (HC) is one of the basic biometric parameters used to assess fetal size. HC together with biparietal diameter (BPD), abdominal circumference (AC), and femur length (FL) are computed to produce an estimate of fetal weight. In the second trimester, this may be extrapolated to an estimate of gestational age and an estimated due date (EDD).

Measurement technique

HC is measured on the same plane as BPD, that is on an axial plane that traverses the thalami and cavum septum pellucidum.
transducer must be perpendicular to the central axis of the head, and thus the hemispheres and calvaria should appear symmetric.
cerebellar hemispheres should not be in the plane of the image, or the probe is too caudal giving an inaccurate size of the fetal head.

If the available ultrasound equipment allows for measurement of an ellipse, this may be drawn around the outside of the calvarium. Alternatively, HC may be calculated from BPD and occipitofrontal diameter (OFD) as: HC = 1.62 × (BPD + OFD) ³.