This current page has images of Carnegie stage 1 to 23 of Human embryonic
development organized as a table showing dates and features for each stage.
Stages are based on the external and/or internal morphological development of the
embryo, and are not directly dependent on either age or size. The human embryonic
period proper is divided into 23 Carnegie stages. Criteria beyond morphological features
include age in days, number of somites present, and embryonic length. (about Carnegie)
Note that images are not to scale.
Related Stage pages: Carnegie Stage page with larger images of each stage. Week by
week timeline of human development showing key features with links to other resources.
Carnegie Stage Posters poster versions (in preparation) of the human carnegie stages.
Clicking on the small image will open a large image version of that stage.
To see the various staging systems for each species look at the Embryo Staging Systems
references.
Carnegie Stage Table
Stage
Days
(approx)
Images
Size (mm) (not to scale, click image to
Events
see original)
1
1
0.1-0.15
(week 1)
fertilized oocyte, pronuclei
cell division with reduction
2
2-3
0.1-0.2
in cytoplasmic volume,
formation of inner and
outer cell mass
3
4-5
0.1-0.2
4
5-6
0.1-0.2
5
7 - 12
(week 2)
0.1-0.2
loss of zona pellucida,
free blastocyst
attaching blastocyst
implantation
extraembryonic
6
13 - 15
0.2
mesoderm, primitive
streak
15 - 17
7
0.4
(week 3)
8
17 - 19
1.0 - 1.5
gastrulation, notochordal
process
primitive pit, notochordal
canal
Somite Number 1 - 3
9
19 - 21
1.5 - 2.5
neural folds, cardiac
primordium, head fold
22 - 23
10
Somite Number 4 - 12
2 - 3.5
(week 4)
neural fold fuses
Somite Number 13 - 20
11
23 - 26
2.5 - 4.5
rostral neuropore closes
Somite Number 21 - 29
12
26 - 30
3-5
caudal neuropore closes
Somite Number 30
28 - 32
13
4-6
(week 5)
leg buds, lens placode,
pharyngeal arches
Stage 13/14 shown in serial embryo sections series of Embryology Program
14
31 - 35
5-7
15
35 - 38
7-9
8 - 11
(week 6)
17
42 - 44
lens vesicle, nasal pit,
hand plate
nasal pits moved
37 - 42
16
lens pit, optic cup
ventrally, auricular
hillocks, foot plate
11 - 14
finger rays
44 - 48
18
13 - 17
ossification commences
16 - 18
straightening of trunk
(week 7)
19
48 - 51
51 - 53
20
18 - 22
(week 8)
21
53 - 54
22 - 24
upper limbs longer and
bent at elbow
hands and feet turned
inward
Stage 22 shown in serial embryo sections series of Embryology Program
22
54 - 56
23 - 28
23
56 - 60
27 - 31
eyelids, external ears
rounded head, body and
limbs
Following this stage Fetal Development occurs until birth (approx 40 weeks)
(Source: Rothenburger and Gay, 1995. and others)
References
Search Pubmed Now: Human[TITL]+embryo[WORD]+stages[WORD]

Nishimura H, et al.
[See Related Articles] Normal
development of early human embryos: observation of
90 specimens at Carnegie stages 7 to 13. Teratology.
1974 Aug;10(1):1-5.

O'Rahilly R.
[See Related Articles] Early human
development and the chief sources of information on
staged human embryos. Eur J Obstet Gynecol Reprod
Biol. 1979 Aug;9(4):273-80

O'Rahilly R.
[See Related Articles] Guide to the staging
of human embryos. Anat Anz. 1972;130(5):556-9.

Gaubert-Cristol R, et al.
[See Related Articles] [End of
embryonic somite period in the rat and a comparison
with the corresponding embryonic period in humans].
Bull Assoc Anat (Nancy). 1991 Sep;75(230):55-9.
French.