The document provides an overview of fetal development from the third month until birth, detailing key milestones in size and weight as well as the development of organs and systems. It discusses the formation of the umbilical cord, placenta, and the protective role of amniotic fluid, along with potential complications such as low birth weight and various abnormalities. Additionally, it covers prenatal diagnostic techniques and emphasizes the significance of careful monitoring during gestation.

1. Fetal period
3rd month IUL to end of birth

2. 9th week
38th week

3. Characterized by
1. Maturation of tissues & organs
2. Rapid growth of body

4. Fetal Development
10th week
12th week
16th week
20th week/5M
28th week/7M
32th week/8M
36th week/9M
u
Upper limbs &
f
Formed

5. • Age 5-12weeks CRL-5-8cms;
Weight- 10-45g
• Age 15-20weeks, CRL-15-20cms;
Weight- 250-450g.
• Age 30-32weeks, CRL-28-30cms;
Weight- 1400-2100g
• Age 36-38weeks, CRL-36cms;
Weight- 3000-3400g

6. • Length of Pregnancy 280days or 40 weeks
after the onset of last normal menstrual
period (LNMP) .
• Accurately 266days or 38weeks after
Fertilization.

7. • Growth in length is particularly striking
during 3rd 4th & 5th month of gestation.
• Increase in weight is most striking during
last 2 months(8th & 9th month) of gestation.

8. • Malformation
are predominant
during 3rd to 8th
week of
development
(organogenesis)
• It is crucial
period for the
embryo.

9. Few malformations also arise during
Fetal period mainly due to mechanical
forces leading to intrauterine
compression.

10. • 1. Slow growth of Head compared to rest body.
• 2. Face is more human looking.
• 3. Eyes come to lie ventrally & Ears attain
definitive position.
• 4.Limbs reach relative length due to development
of Primary centers of ossification : 8-12th week.
3rd month :
(9th -12th week)

11. 12
5.External Genitalia develops
Sex of fetus can be determined in
3rd month(12th week)
External
genitalia

12. Female
fetus
Male
fetus
Genital
tubercle
/Penis

13. 4th & 5th months (16-20 weeks)
• 1.Fetus is covered with fine hair known Lanugo
• 2. Hair visible in eyebrows & head.
• 3. Fetus lengths rapidly.
• 4. Suckling of thumb
Lanugo

14. 6.Movements of fetus can be
felt during 5th month (20weeks)
by Mother Quickening
Quickening

16. • 1. Several organs system are able to function.
• 2. Respiratory system & CNS have not differentiated
sufficiently .
• 3.Coordination b/w the two systems not yet established.
• 4. Fetus born during 6th month is difficult to survive.

17. 4. 6th month (24weeks) :Weight increases.
5. Skin of Fetus: is reddish & wrinkled
because of lack of underlying connective
tissue.
Weight increases
24 WEEKS

18. 7th to 8th month:(28-32 weeks)
1. Skin covered with whitish fatty substance known as Vernix
caseosa composed of secretory products of sebaceous glands.
Vernix caseosa protects fetal skin from the amniotic fluid.
Traces of the substance may appear on skin after birth
Vernix caseosa

19. 7th to 8th month (28-32Weeks)
2. Fetus obtains well rounded contours as a
result of deposition of subcutaneous fat.
3. Foetus born at 7th month (28weeks).
Has 90% chance of surviving.
Subcutaneous fat

20. •1.Weight : 3000- 3400gms.
•2. CHL: 45-50cms

21. Skull has largest circumference of all
parts of body an important fact helps
in passage thro’ birth canal
9th month
(36-40 weeks)
Birth canal

22. 9th month/36-40 weeks
Sexual characteristic
are more pronounced :
Testes in scrotum

23. Date of birth is most accurately indicated as 266 days
or 38 weeks after fertilization
Obstetrician calculates date of birth as 280 days or 40
weeks from first day LMP
Most of fetuses are born within 10-14 days of
calculated delivered date.

24. • If they are born earlier  premature
(32weeks)
• If born later post mature (42weeks)
• Valuable tool for assisting the age
determination is by Ultra sound

25. Clinical correlation
Low birth weight( 2.500g)
• 1.Length & weight are genetically determined, but
environmental factors also play important role.
• Intrauterine growth restriction(IUGR) .
• These infants are pathologically small.
• 2.Have neurological deficiencies & congenital
malformations
• 3.Common in maternal nutritional status and others
like multiple birth (twins, triplets)

26. Prenatal screening techniques
Prenatal diagnosis
Under Ultra sonography
•1.Amnionocenetesis
•2.Chorionic villous sampling.
These Tests determine
1.Placental Growth
2. Fetal growth.
3.Congenital malformation
4.Chromosomal abnormalities.

27. 14-16 WEEKS 8-10 WEEKS

29. PLACENTA

30. I. UMBILICAL CORD
Long ,twisted beaded
1-2cms in diameter, 30-90cms in length
Umbilical cord

31. Umbilical cord is the life line
that connects the fetus to its
mother.
Umbilical cord

32. Umbilical cord has smooth surface because it is
covered by amnion
Umbilical cord

33. UMBILICAL CORD
Placenta
At full term 1.One end of the cord is attached to center of
anterior abdominal wall of the fetus.
2.Other end is fixed to the fetal surface of placenta
Tubular cord enveloped by Amniotic membrane

34. 5th week structures pass thro’ the primitive umbilical ring(5).
• 1.Umbilical cord Umbilical vessels : 2 umbilical arteries & 1
umbilical vein).
• 2.Yolk stalk ( vitelline intestinal duct) & vitelline vessels.
• 3. Distal part of Allantois.
2UA&1UV
Yolk Stalk
Primitive Umbilical ring

35. • 4. Intestinal loops(physiology hernia
5- 10 Weeks)
• Enters back to abdominal cavity by
10week
Intestinal
loops

36. Contents of Umbilical cord at full term
• Two umbilical arteries .
• Convey deoxygenated
blood from fetus mother.
• One umbilical vein early
in pregnancy veins are two
later rt. Umbilical vein
disappears & left U V
persists & carries
oxygenated blood from
placenta  fetus
2-UA
1-LUV

37. After birth umbilical cord is ligated

38. The circulation of blood in umbilical arteries is first
stopped by reflex spasm of muscular wall, followed
by cessation of blood flow in the vein

39. Short cord
Short cord may cause difficulty during delivery by
pulling the placenta from its attachment in the
uterus (premature separation)
Clinical correlation of umbilical cord
Normal
umbilical
cord

40. Extremely long cord may encircle the neck of fetus
:strangulation & hypoxia of fetus
Normal
umbilical
cord
Long cord

41. Cord prolapse
long cord compressed b/w head of
fetus & Pelvic wall of mother
leading to hypoxia of Fetus
Cord prolapse

42. • One umbilical artery & one umbilical vein
is associated with Cardio vascular defects
& other anomalies.
Abnormal

43. Applied
•Colour flow Doppler
Ultrasonography may be used
for prenatal diagnosis of
abnormalities of umbilical
cord & its vessels.

44. 2. Amnion
Extraembryonic membrane that
surrounds the fetus, protects it from
external shocks or jolts

45. Development :Amniotic sac appears
during 2nd week of development

46. • Amniotic fluid is Clear & watery & produced
• by amniotic cells
Amniotic
cavity

47. • Amount of Amniotic fluid increases from
• 30ml at 10 weeks
• 450ml at 20weeks
• 800-1000ml at 38 weeks(at term)

48. • Fetus is suspended by its umbilical cord
in the amniotic fluid which acts as
protective cushion
Umbilical cord
Amniotic fluid
Fetus

49. Factors regulating the volume
of Liquor amnoii
• Beginning of 5th month fetus swallows its
own amniotic fluid about 400ml a day
• It is absorbed by gut, then into blood
stream.
• It then passes to maternal blood via
placenta.
• Fetal urine is added daily to the amniotic
fluid from 5th month by fetal kidney, but
this urine is mostly water, because the
placenta functions as an exchange for
metabolic wastes.

50. • Absorbs jolts of fetus &
prevents injuries.
• Prevents adherence of embryo to the
amnion.
• Allows free movements of fetus aiding
muscular development
• Maintains symmetrical external growth
and differentiation of delicate tissues of
embryo & mainly lung growth
• Assists in maintaining homeostasis of
fluid & electrolytes.
Functions
Normal :1000ml-1200 ml

51. Abnormalities of liquor amnoii
• Polyhydramnios
(Hydramnios) –
high volume of amniotic
fluid exceeds more than
2 litres.
• A)It occurs when fetus is
unable to swallow in
esophageal atresia or
B)Anencephaly
(swallowing reflex is
absent)
• C)Maternal diabetes.
Polyhydramnios

52. • Oligohydramnios:
decreased amount
of fluid less than
400ml. It may be
due renal agenesis.
• Oligohydramnios
causes
1. Club foot
2. Lung hypoplasia
3.Facial defects
Oligohydramnios

53. •Premature rupture
of amnion, is
common cause of
preterm labour.
•Causes of rupture
sometimes may be
due to trauma.
Premature rupture

54. • Amniotic bands is due infections & toxins. They
form rings around the limbs & fingers causing
physiological amputation of the part
Amniotic band syndrome

55. Clinical importance
• Amniocentesis : aspiration of
amniotic fluid through cervix or
anterior abdominal wall.
• Nuclear sexing of fetus in sex
linked diseases.
• Estimation of enzymes in case
of gross fetal malformations.

56. 3.Yolk sac formed during 2nd week
1.Primary:10th day
2. Secondary :14th day
3. Definitive Yolk sac : 3rd week
Primary
Yolk sac
Secondary
Yolk sac

57. As the result of Cephalo caudal folds & lateral folds
large portions of endodermal germ layer & yolk sac
is incorporated into body of embryo to form gut tube
Flattened trilaminar germ disc
Primitive gut tube

58. The portion of Yolk sac not taken up by
embryo is termed as Definitive yolk sac
Definitive
Yolk sac

59. Function /Role
of yolk sac
Nutritive organ during early stages prior to
development of blood vessels.
Hemopoiesis &Contributes for first blood
cells.
 Forms Primitive gut(4th week) &
Respiratory system
 Provide Primordial germ cells

60. 4.Allantoic diverticulum
• Allantoic diverticulum(3rd week) arises
from ventral wall of hindgut & forms
Endodermal cloaca.
Allantois
Hindgut

61. 5. Chorion: 2nd week Derived from
EEM
Chorion is one of the membranes that
surround the fetus: Nutrition
Coelomic cavity

62. Chorion 2 main Functions:
1.Chorionic fluid in chorionic cavity protects
the embryo
2. Chorion villi which are extensions of the
chorion that pass through the uterine decidua
and connect with the maternal blood vessels.

63. Chorion tertiary villi differentiates :
Chorionic Frondosum (Placenta)overlapped by
Decidua Basalis
Chorionic Laeve(degenerates) overlapped by
Decidua capusularis

64. Clinical correlation
Chorionic villous biopsy is done to detect
Genetic disorders in the fetus
8-10 WEEKS

65. 11
11. Umbilical cord

66. Eutherian Mammals Possess Placenta
Human Placenta Is Discoid, Haemochorial
& Deciduate

67. Placenta-Highly Vascular
Attached to Uterine wall & establishes connection
b/w Mother & Fetus via Umbilical cord
Human Placenta
Umbilical
cord
Uterine wall
Fetus

68. Placenta in Latin means “a flat cake”
In mammals develop during pregnancy.
Fetomaternal Organ

69. • Human placenta is Discoid,
Haemochorial and Deciduate which
connects the Fetus with uterine wall
of the Mother.
Discoid

70. • Placental Structure has Maternal & Fetal
tissues that come direct contact without
rejection suggesting immunological
acceptance.
Maternal
surface
Fetal
surface

71. • Shortly after birth of fetus, placenta &
fetal membranes are expelled from the
uterus
Placenta

72. EMBRYOBLAST
TROPHOBLAST
Embryoblast forms the Embryo proper
Blastocyst:
5th -6th day

73. Development of Human Placenta
Two sources
Foetal part
Trophoblast &
extra embryonic
mesoderm
Chorionic
frondosum.
• Maternal part
Uterine
endometrium 
Decidua basalis
Chorionic
frondosum
Decidua
basalis

74. Placental development starts as soon as the Blastocyst
gets Implanted into endometrium :
1. 7th day (1 week)& is completed by 12th week/3month
2.Two layers of Trophoblast Multilayer
Syncytiotrophoblast & Mononuclear Cytotrophoblast
3.Syncytiotrophoblast: Utero- Placental circulation

75. Changes in the Trophoblast- 3rd week
Primary, secondary & tertiary Villi

76. Plate
Villi projection from chorion
is chorionic villi.

77. • Villi extend from chorionic plate to Decidual plate
• (D. basalis) are stem villi or Anchoring villi.
• Those that branch from the sides of stem villi are Floating villi

78. Extra embryonic vascular system is first
formed which later communicates with
intra embryonic vascular system & Heart by
end of 3rd week (22nd day).
Extra embryonic
vascular system
Intra embryonic
vascular system
Primordial
Heart

79. • Capillaries in tertiary villi make contact with capillaries developing in
mesoderm of chorionic plate & with blood vessels the connecting stalk.
• Vessels of connecting stalk establish connection with intra embryonic
circulating system which is also simultaneously developing.
• .
End of 3rd week: The villous system ready to supply
the embryo proper with essentials & nutrients
Chorionic
Plate

80. Villous system
of Trophoblast
is ready to
supply nutrients
& O2 to embryo
by 21st -22nd day
Heart beats on
22nd day.
Chorionic villous biopsy is done to detect
genetic disorders in the fetus
Villous system

81. Early weeks of development(3rd week) villi covers
entire surface of Chorion & as pregnancy advances
villi are more pounced at embryonic pole
Embryonic
pole

82. • As pregnancy
advances villi are
more pounced at
embryonic pole &
continue to grow
& expand give it a
bushy
appearance
Chorionic
Frondosum
Chorionic
Frondosum

83. • Villi at embryonic
pole
• Chorionic
• Frondosum
• Villi at
abembryonic pole
degenerate.
• Chorionic Laeve
• 3rd month/12
weeks
Chorionic
Frondosum
bushy
Chorionic
Laeve

84. End of 3rd week of development End of 4th week of development

85. Chorionic frondosum overlapped by
Decidua Basalis
( abundant lipid & glycogen).
Chorionic laeve (less) Decidua Capsularis

86. CHORIONIC PLATE
DECIDUAL PLATE

87. • With increase in size of chorionic cavity,
D.Capsularis is stretched & degenerated &
subsequently Chorionic Laeve comes in contact
with D. Parietalis.
• On the opposite side of uterus the two fuse
thereby obliterating the uterine lumen.
D. Parietalis
lumen
Chorionic
laeve
D. Capsularis
Chorionic
cavity

88. • Only portion of chorion participating in
exchange process is Chorionic
Frondosum& Decidua Basalis which make
up the placenta.
Chorionic
Frondosum
Decidua Basalis
Uterine cavity
Placenta

89. • Amniotic cavity also enlarges obliterating chorionic
cavity leading to Fusion of amnion & chorion
together & form amnion-chorionic membrane. It is
this membrane that ruptures during labor. (breaking
of water)
amnion-
chorionic
membrane.

90. Structure of Placenta
4month(16weeks)2 components
Foetal part: Chorionic frondosum
Maternal part: Decidua basalis
On foetal side placenta is bordered by chorionic
plate, on the maternal side is decidua basalis ,
(Decidua plate)
Foetal part:
Chorionic Frondosum
Maternal part:
Decidua Basalis
Chorionic plate

91. • b/w Chorionic plate & Decidual plate are
Intervillous spaces filled with maternal
blood in which are floating villi.
Intervillous
spaces

92. • 4th MONTH  decidua septa projects
into Intervillous spaces but do not reach
chorionic plate.
• As result of septum placenta is divided
by number of compartment the
cotyledons.
Chorionic plate
Cotyledons
Decidua septa

93. Placental surface area is parallel to
expanding uterus, through out
pregnancy.
Covers 15-30% of internal surface of
uterus.

94. • From stem villi(tertiary villi) branch
floating villi which project in to
Intervillous spaces.
• Terminal villi form functional units of
placenta.
Tertiary villous/
Stem Villi
Floating villi/
Terminal villi

95. • Each terminal villi is covered by 2 layers of
trophoblast i.e. inner cytotrophoblast & outer
Syncytiotrophoblast.
• Central core of villous
• 1.1-6 Fetal capillaries
• 2. Stromal cells / Primitive Mesenchymal cells
3.Reniform Hofbauer cells (phagocytic)

96. • Early part (3 Month) of pregnancy about 800-
1000 stem villi radiate from entire chorionic
wall.
• Later with regression of chorionic laeve
(4 Month) only 60 stem villi persist in Human
placenta.
Early part Later part
Chorionic
villi

97. Maternal cotyledons are 15-30 in number
Each cotyledon contains 2-4 stem villi
with 2-4 fetal capillaries.
Cotyledons
2-4 stem villi

98. Adult placenta

99. MACROSCOPIC APPEARANCE OF PLACENTA
Foetal surface Maternal surface
Foetal surface Maternal surface

100. Full term placenta : Discoid
diameter 15-25 cms, 3cm thick
weighs 500 to 600g.
• At birth torn from uterine
wall, approximately
30minutes after birth of the
child & is expelled from the
uterine cavity
• Two surfaces
• 1.Foetal surface covered by
chorionic plate .
• 2.Maternal surface
irregular with 15-30
cotyledons
• 3.Peripheral margin.
F
M

101. • Foetal surface: Large number arteries &
veins converge toward the umbilical cord.
• Attachment of umbilical cord is usually
eccentric or marginal.

102. • Maternal surface: rough, irregular
with 15-30 cotyledons covered by
decidua basalis.
F M
M

103. placental
Placental
Circulation
placental
Utero-
Placental
Circulation
placental
Feto -
Placental
Circulation

104. Umbilical vein
Umbilical arteries
Fetal circulation
Maternal circulation
Endometrial veins & arteries
Placenta at Term

105. Placental circulation
• Umbilical Arteries(2) Chorionic arteries 
intervillous spaces Endometrial veins Mother.
• Mother Endometrial arteries IVS Chorionic
veins Umbilical vein
UA(2)
CA EV
EA
CV
UV
IVS
IVS

106. About 600ml of Maternal blood circulates
through the Intervillous spaces / min.
IVS

107. • Volume of Intervillous spaces is 150 ml.
• Blood within the space therefore
exchanged 4 times per min.
Intervillous
spaces

108. Placental Membrane(barrier)
which separates maternal blood from fetal
blood
• Early: 0.025mm: 4 layers(up to 4 month)
• Later: 0.002mm: 2 layers (5 month onwards)
In early(4M)
pregnancy
In later
pregnancy

109. • 1.Placenta succenturiate
• Accessory placenta
connected to main
placenta by Foetal
membrane
• 2.Battle Dore Placenta
• Umbilical cord attached
close to margin of
placenta.
• 3.Velamentous Placenta
• Cord fails to reach the
placenta & attached to
Foetal membranes
Types of Placenta
1.
2.
3.

110. Battle Dore placenta
Velamentous Placenta
Placenta succenturiate

111. Abnormal Site of implantation
Placenta previa
lower part of uterus
serious bleeding during parturition
Placenta
previa

112. Abruption placenta
Premature separation of placenta

113. Degree of adhesion
• Placenta Accreta 
adhered to D.
Basalis.
• Placenta Increta 
penetrates into
myometrium.
• Placenta percreta
penetrates into
uterine wall

114. Clinical Correlation

115. Erythroblastosis fetalis
& Fetal Hydrops
Fetal red blood cells antigens
cross the placental barrier &
stimulate maternal antibody
These antibodies will attack &
hemolyze fetal cells resulting in
hemolytic disease in the new born
Erythroblastosis fetalis
Anaemia leads to edema
Fetal Hydrops leading to fetal
death
Clinical correlation