EXTERNAL APPEARANCE
DURING SECOND MONTH
Your Logo
CROWN RUMP LENGTH CORRELATED TO AGE
IN WEEKS
CRL (mm)
AGE (WEEKS)
5-8
5
10-14
6
17-22
7
28-30
8
 During 2nd month size of head
increases and the limbs, face,
ears, nose and eyes form.
 By the beginning of the 5th
week, forelimbs and hind
limbs appear as paddle
shaped buds.
 The forelimb buds are located
dorsal to the pericardial
swelling at the level of the C4
– T1 somites
 Hind limb buds appear at the
level of the lumbar and upper
sacral somites
CRL= 9.8mm; 5th week
Forelimbs Paddle shaped
 Terminal portions of buds flatten and
1st circular constriction separates
them from proximal more cylindrical
segments
 Soon 4 radial grooves separates 5
slightly thicker areas appearing on the
distal portion of buds
 These grooves are called rays which
appear in hand region first and shortly
afterwards in foot
 Upper limb is slightly more
advanced in development than
lower limb
 While fingers and toes are formed 2nd
constriction divides the proximal
portion of buds into two segments and
3 characteristic features of adult
extremity are recognizable
CRL=13mm; 6th week
CRL=21mm; 7th week chorionic sac open, embryo in amniotic cavity
Compare the size of head with the rest of body
CRL= 25mm; 7th to 8th week embryo. Chorion and amnion have been opened
Size of head, the eye, auricle and well formed face. Physiological umbilical herniation
BIRTH DEFECTS
Most major organs and organ systems are formed
during the 3rd to 8th week. This period is called the
period of organogenesis. Stem cell populations
are establishing each of the organ primordia, any
insult from genetic and environmental influences can
result in birth defects. The 3rd and 4th weeks are
particularly vulnerable.
HUMAN FETAL PERIOD
BY
Your Logo
DR SAMINA ANJUM
PERIOD OF FETUS
The period from the beginning of the 9th
week to birth is known as Fetal period.
Tissue and organs mature; become
competent to assume their specialized
functions.
Rapid growth of body
Transformation of embryo to fetus is gradual.
CRL or CHL
Growth in length is particularly striking during the
3rd, 4th and 5th months
 While increase in weight is most striking during the
last 2 months of gestation.
LENGTH OF PREGNANCY
280 days or 40 weeks from LNMP
266 days or 38 weeks after fertilization
MONTHLY CHANGES
The growth of the head
during fetal period is slow
compared to the rest of
body.
At the beginning of 3rd
month, the head
constitutes approximately
½ of crown – rump
length (CRL).
By the beginning of 5th
month, the size of the head
is about 1/3rd of crown –
heel length (CHL)
At birth the size of the head
is approximately 1/4th of
CHL.
THIRD MONTH (9-12 wks)
FACE: More human looking broad
HEAD:
Disproportionately large
Makes up nearly half of the fetus'
size
EYES:
Directed ventrally
Eyelids fused
EARS:
Rise to their definitive position on the
side of head
LIMBS: Reach their relative length
PRIMARY OSSIFICATION CENTERS: Are
present in the long bones and skull by the 12th
week.
PREUMBLICAL HERNIATION: During the 6th week,
intestinal loops cause a large swelling (physiological
herniation) in the umbilical cord.
By the 12th week, loops withdraw into the abdominal cavity.
11th week fetus: Intestines are no longer in the
umbilical cord
ERYTHROPOIESIS, : At 9th week liver is the major
site, after 12th week activity is reduced and begins in
spleen
EXTERNAL GENITALIA: Appear well differentiated
MUSCULAR ACTIVITY: Evoked in aborted fetuses
SWALLOWING REFLEX: 10 WEEKS
4TH AND 5TH MONTHS
 During the 4th and 5th months, the
fetus lengthens rapidly and at the end
of first half of intrauterine life, its CRL
is approximately 15cm, about ½ the
total length of newborn.
 Weight is less than 500 gm
Fine hair (LANUGO)
Head and eye brow hair are visible
Fetal movements felt by mother
(QUICKENING)
6TH AND 7TH MONTHS
 During the 2nd half of IUL,
weight increases
considerably and
particularly during last 2.5
months, when 50% of the
full term weight (approx.
3200gms) is added.
 During the 6th month, the
skin of the fetus is reddish
and has wrinkled
appearance because of the
lack of underlying
connective tissue.
The respiratory and the central nervous system have
not differentiated sufficiently, and coordination
between the two systems is not yet well developed.
By 6.5 to 7 months, fetus has length of about 25 cm
and weighs approximately 1100gms.
If born at this time, the infant has a 90% chance of
surviving.
Sucking movements
Some sounds can be heard
Eyes are sensitive to light
NINTH MONTH (33-36 wks)
SKIN:
Dull redness of the skin fades
Wrinkles smooth out
Lanugo begins to disappear
BODY AND LIMBS:
Become rounded
Deposition of subcutaneous
fat
VERNIX CASEOSA: By the end of IUL, the skin is
covered by a whitish fatty substance
At the end of 9th month,
the skull has the largest
circumference of all parts
of the body.
At the time of birth, the
weight of a normal fetus
is 3000 to 3400gms, its
CRL is about 36cms,
and its CHL is about
50cms.
Testes should be in the
scrotum (end of 9th
month)
GROWTH IN LENGTH & WEIGHT
DURING FETAL PERIOD
Age (weeks)
CRL (cm)
Weight (g)
9 -12
5-8
10 - 45
13 - 16
9 - 14
60 - 200
17 - 20
15 - 19
250 - 450
21 - 24
20 - 23
500 - 820
25 - 28
24 - 27
900 - 1300
29 - 32
28 - 30
1400 - 2100
33 - 36
31 - 34
2200 - 2900
37 - 38
35 - 36
3000 - 3400
DEVELOPMENTAL HORIZONS
DURING FETAL LIFE
EVENTS
AGE (weeks)
Taste buds appear
7
Swallowing
10
Respiratory movements
14 – 16
Sucking movements
24
Some sounds can be heard
24 – 26
Eyes sensitive to light
28
MEASUREMENTS AND CHARACTERISTICS
OF FETUSES
 Various measurements and external characteristics are
useful for estimating fetal age.
 Until the end of first trimester, CRL is the method of choice.
 In the second and third trimesters, several structures can be
identified and measured ultrasonographically
 Gestational sac appear on transabdominal sonography at 5th
week and approx a week earlier by TVS .
ULTRASONOGRAPHY MEASUREMENTS
 BPD
 Head circumference
 Abdominal circumference
 Femur length
 Foot length
 Fetal weight
CROWN RUMP LENGTH
BI-PARIETAL DIAMETER
CIRCUMFERENE
FEMUR LENGTH
FOOT LENGTH
FACTORS INFLUENCING FETAL GROWTH
Following factors stimulate fetal growth:
 Glucose
 Aminoacids
 Insulin (secreted by fetal pancreas)
 Insulin like growth factors
 Human growth hormone