PCW / GW / CRL / CS

Info needed be checked

PCW and GW

 

Defination of different chronology calibrations in human development

PCW   post conception week  the eaiset notion

GW    Gestation week Basically two weeks more than PCW since ⬇

The unborn baby spends around 38 weeks in the womb, but the average length of pregnancy (gestation) is counted as 40 weeks. This is because pregnancy is counted from the first day of the woman's last period, not the date of conception, which generally occurs two weeks later.

by the way human pregnancy typically takes 38-40 gw (which means 36-38 PCW). Baby borned before 37 gw will be considered as premature.

 

CS

Carnegie stages (CS) are a standardized system of 23 stages used to provide a unified developmental chronology of the vertebrate embryo.

The stages are delineated through the development of structures, not by size or the number of days of development, and so the chronology can vary between species, and to a certain extent between embryos. In the human being only the first 60 days of development are covered by carnegie stages; at that point, the term embryo is usually replaced with the term fetus. (see figure above) 

 

                                           

GW PCW post-conceptual days carnegie stage    
1          
2   0      
3 1 7 5    
4 2 14 6    
5 3 21 9    
6 4 28 12    
7 5 35 14    
8 6 42 17    
9 7 49 19    
10 8 56 22    
11 9 63      
12 10 70      
13 11 77      
14 12 84      
15 13 91      
16 14 98      
17 15 105      
18 16 112      
19 17 119      
20 18 126      
21 19 133      
22 20 140      
23 21 147      
24 22 154      
25 23 161      
26 24 168      
27 25 175      
28 26 182      
29 27 189      
30 28 196      
31 29 203      
32 30 210      
33 31 217      
34 32 224      
35 33 231      
36 34 238      
37 35 245      
38 36 252      
39 37 259   expected term of birth
40 38 266   expected term of birth
41 39 273      
42 40 280      

So that is why the CS12 will be considered as GW6 in kriegstein (ke + rig + s + tein) paper 

 

CRL

Crown rump length (CRL) is the length of the embryo or fetus from the top of its head to bottom of torso. It is the most accurate estimation of gestational age in early pregnancy, because there is little biological variability at that time.

CRL is measured as the largest dimension of embryo, excluding the yolk sac and extremities. It is used as a primary measure of gestational age between 6-13 weeks. After 13 weeks, head circumference, biparietal diameter, and femur length measurements become more useful measurements for assessing fetal growth.