The measurement of the thoracic circumference is taken transversely at the level in which a four chambered heart can be visualized.
The circumference of the thorax can be measured:
(1) directly using computer planimeters
(2) indirectly from measurement of the anteroposterior diameter and the maximum transverse diameter at right angles to the anteroposterior axis, as follows:
thoracic circumference in cm =
= 0.5 ((anteroposterior diameter in cm) + (transverse diameter in cm)) * π
Fetal thoracic circumference
|
week |
50th percentile |
5th percentile |
95th percentile |
|
16 |
9.1 cm |
6.4 cm |
11.9 cm |
|
17 |
10 cm |
7.3 cm |
12.8 cm |
|
18 |
11 cm |
8.2 cm |
13.7 cm |
|
19 |
11.9 cm |
9.1 cm |
14.6 cm |
|
20 |
12.8 cm |
10 cm |
15.5 cm |
|
21 |
13.7 cm |
11 cm |
16.4 cm |
|
22 |
14.6 cm |
11.9 cm |
17.3 cm |
|
23 |
15.5 cm |
12.8 cm |
18.2 cm |
|
24 |
16.4 cm |
13.7 cm |
19.1 cm |
|
25 |
17.3 cm |
14.6 cm |
20 cm |
|
26 |
18.2 cm |
15.5 cm |
21 cm |
|
27 |
19.1 cm |
16.4 cm |
21.9 cm |
|
28 |
20 cm |
17.3 cm |
22.8 cm |
|
29 |
21 cm |
18.2 cm |
23.7 cm |
|
30 |
21.9 cm |
19.1 cm |
24.6 cm |
|
31 |
22.8 cm |
20 cm |
25.5 cm |
|
32 |
23.7 cm |
20.9 cm |
26.4 cm |
|
33 |
24.6 cm |
21.8 cm |
27.3 cm |
|
34 |
25.5 cm |
22.8 cm |
28.2 cm |
|
35 |
26.4 cm |
23.7 cm |
29.1 cm |
|
36 |
27.3 cm |
24.6 cm |
30 cm |
|
37 |
28.2 cm |
25.5 cm |
30.9 cm |
|
38 |
29.1 cm |
26.4 cm |
31.9 cm |
|
39 |
30 cm |
27.3 cm |
32.8 cm |
|
40 |
30.9 cm |
28.2 cm |
33.7 cm |
from Chitkara (1987)
When this data is analyzed in JMP, the following equations are obtained:
50th percentile for thoracic circumference in cm =
= (0.9077692 * (week of gestation)) - 5.377538
5th percentile for thoracic circumference in cm =
= (0.9086923 * (week of gestation)) - 8.135385
95th percentile for thoracic circumference in cm =
= (0.9083077 * (week of gestation)) - 2.660615
week of gestation =
= (1.1015794 * (50th percentile thoracic circumference in cm)) + 5.9243484
= (1.1004618 * (5th percentile thoracic circumference in cm)) + 8.9532066
= (1.1009273 * (95th percentile thoracic circumference in cm)) + 2.926839
Specialty: Obstetrics & Gynecology, Pedatrics
ICD-10: ,
