Fetal Staging System

Post Conception Weeks (PCW)

Foot Length (mm)

Knee to Heel Length (mm)

Gestational Age in Weeks

Above 5 and less than 6
8
10

6 or above and less than 8

11
11
8 or above and less than 10
13
12
10 or above and less than 13
17

13

12
13 or above and less than 17
24
14
17 or above and less than 20
31
15
14
20 or above and less than 23
36
16
15
23 or above and less than 25
 
40

17

16
25 or above and less than 27
 
43
18
17
27 or above and less than 31
 
51
19
18
31 or above and less than 33
 
56
20
19
33 or above and less than 36
 
60
21
20
36 or above and less than 40
 
66
22

W.M. Hern. Correlation of Fetal Age and Measurements between 10 and 26 weeks of Gestation, Obstetrics and Gynecology. Vol 63, No1, 26-32, January 1984.