It can be used during the second and third trimesters.
The head circumference is less affected by alterations in the shape of the infant's head than the biparietal diameter, and as such is superior for estimating fetal weight.
It can be determined:
• directly using computer planimeters
• indirectly from measurement of the occipitofrontal and transverse dimension, as follows:
head circumference in cm =
= 0.5 ((occipitofrontal dimension in cm) + (transverse dimension in cm)) * π
|
menstrual age in weeks |
head circumference in cm |
|
12 |
6.8 |
|
12.5 |
7.5 |
|
13 |
8.2 |
|
13.5 |
8.9 |
|
14 |
9.7 |
|
14.5 |
10.4 |
|
15 |
11 |
|
15.5 |
11.7 |
|
16 |
12.4 |
|
16.5 |
13.1 |
|
17 |
13.8 |
|
17.5 |
14.4 |
|
18 |
15.1 |
|
18.5 |
15.8 |
|
19 |
16.4 |
|
19.5 |
17 |
|
20 |
17.7 |
|
20.5 |
18.3 |
|
21 |
18.9 |
|
21.5 |
19.5 |
|
22 |
20.1 |
|
22.5 |
20.7 |
|
23 |
21.3 |
|
23.5 |
21.9 |
|
24 |
22.4 |
|
24.5 |
23 |
|
25 |
23.5 |
|
25.5 |
24.1 |
|
26 |
24.6 |
|
26.5 |
25.1 |
|
27 |
25.6 |
|
27.5 |
26.1 |
|
28 |
26.6 |
|
28.5 |
27.1 |
|
29 |
27.5 |
|
29.5 |
28 |
|
30 |
28.4 |
|
30.5 |
28.8 |
|
31 |
29.3 |
|
31.5 |
29.7 |
|
32 |
30.1 |
|
32.5 |
30.4 |
|
33 |
30.8 |
|
33.5 |
31.2 |
|
34 |
31.5 |
|
34.5 |
31.8 |
|
35 |
32.2 |
|
35.5 |
32.5 |
|
36 |
32.8 |
|
36.5 |
33 |
|
37 |
33.3 |
|
37.5 |
33.5 |
|
38 |
33.8 |
|
38.5 |
34 |
|
39 |
34.2 |
|
39.5 |
34.4 |
|
40 |
34.6 |
from Hadlock (1984)
Equations derived from analysis of this data in JMP:
menstrual age in weeks =
= (0.0009308 * ((head circumference in cm) ^ 3) - (0.041293* ((head circumference in cm) ^ 2) + (1.3292809 * (head circumference in cm)) + 4.2648534
predicted head circumference in cm for given fetal age =
= ((-0.019962 * ((menstrual week gestation) ^ 2) + (2.0495125 * (menstrual week gestation)) - 15.20518
Specialty: Obstetrics & Gynecology, Pedatrics
ICD-10: ,
