The placenta is an organ that develops during pregnancy to allow nutrient, waste, and gas exchange between the mother and fetus. It attaches to the upper uterine wall and consists of fetal and maternal surfaces. The fetal surface has the umbilical cord attachment and visible blood vessels, while the maternal surface is rough and spongy. The placenta performs critical functions like nutrition, gas exchange, waste removal, hormones production, and acts as a barrier between the mother and fetus. Complications can include abnormal attachment or multiple lobes. The amniotic fluid provides protection for the fetus and allows for movement. Its volume peaks at term pregnancy, then decreases, and abnormalities in volume can affect fetal development.

2. PLACENTA.
 Placenta is an organ that connects the developing fetus to
the uterine wall to allow nutrient uptake, waste elimination,
and gas exchange via the mother's blood supply.
 These two, i.e. chorion frondosum and the decidua
basalis form the discrete placenta. It begins
 at 6th week and is completed by 12th week
 Gross anatomy: At term, it is almost a circular disc with a
diameter of 15–20 cm and thickness of about 3 cm at its
center. It thins off toward the edge. It feels spongy and
weighs about 500 gm, the proportion to the weight of the
baby being 1 : 6 at term and occupies about 30% of the
uterine wall. It presents two surfaces,

3. SURAFACES OF PLACENTA
 Fetal surface: The fetal surface is covered by the smooth and
glistening amnion with the umbilical cord attached at or near
its center. Branches of the umbilical vessels are visible
beneath the amnion as they radiate from the insertion of the
cord
 Maternal surface: The maternal surface is rough and
spongy, maternal blood gives it a dull red color. A thin
greyish, somewhat shaggy layer which is the remnant of the
decidua basalis (compact and spongy layer) and has
come away with the placenta, may be visible. Maternal
surface is mapped out into 15–20 convex polygonal areas
known as lobes or cotyledons which are limited by fissures

4. ATTACHMENT AND STRUCTURE CTND
Usually attached to the upper part of the body of the uterus
encroaching to the fundus adjacent to the anterior or
posterior wall with equal frequency.
 The placenta consists of two plates. The chorionic plate
lies internally. It is lined by the amniotic membrane. The
umbilical cord is attached to this plate.
 The basal plate lies to the maternal aspect. Between the
two plates lies the intervillous space containing the stem villi
with their branches, the space being filled with maternal
blood. Amniotic membrane consists of single layer of
cubical epithelium loosely attached to the chorionic plate. It
takes no part in formation of the placenta.

5. MAIN FUNCTIONS
 Transfer of nutrients and waste products between the mother
and fetus. In this respect it attributes ,Respiratory •
Excretory • Nutritive
 Endocrine function: Placenta is an endocrine gland. It
produces both steroid and peptide hormones to maintain
pregnancy
 Barrier function.
 Immunological function.
 Respiratory function: Intake of oxygen and output of
carbon dioxide take place by simple diffusion across the
fetal membrane.
The oxygen supply to the fetus is at the rate of 8
mL/Kg/min and this is achieved with cord blood flow of
165–330 mL/min.

6. FUNCTIONS CTND
 Excretory function: Waste products from the fetus such as
urea, uric acid, and creatinine are excreted to the maternal
blood by simple diffusion.
 Nutritive function: The fetus obtains its nutrients from the
maternal blood and when the diet is inadequate, then only,
depletion of maternal tissue storage occurs
 Immunological, Placental hormones, proteins (SP1), Early
Pregnancy Factor (EPF), PAPP-A, steroids and chorionic
gonadotropin, have got some immunosuppressive effect.
 Villous trophoblasts do not express HLA Class I or Class II
molecules. Extravillous trophoblast (Fig. 3.7)
 only express HLA Class I molecules and no HLA Class II
molecules.

7. ABNORMALITIES
 Bilobate placenta(placenta duplex)In these, the cord inserts
between the two placental lobes—either into a connecting
chorionic bridge or into intervening membranes.
 A placenta containing three or more equally sized lobes is
 rare and termed multilobate. However, more frequently, one
 or more small accessory lobes—succenturiate lobes—may
 develop in the membranes at a distance from the main
placenta, CAN CAUSE PPH WHEN RETAINED DURING 2ND
STAGE OF LABOUR.

8. Placenta accreta, increta, percreta
 Placenta accreta, An invasion of the myometrium which
does not penetrate the entire thickness of the muscle. This
form of the condition accounts for around 75% of all
cases.(75-78%)
Placenta increta, Occurs when the placenta further extends
into the myometrium, penetrating the muscle. 17%
 placenta percreta,The worst form of the condition is when
the placenta penetrates the entire myometrium to the uterine
serosa (invades through entire uterine wall). This variant can
lead to the placenta attaching to other organs such as the
rectum or bladder[2].5-7%

9. THE FETAL MEMBRANES
 Consists of two layers ;outer chorion and the inner
amnion.
 CHORION: It represents the remnant of chorion laeve and
ends at the margin of the placenta. It is thicker than amnion,
friable and shaggy on both the sides. Internally, it is attached
to the amnion by loose areolar tissue externally, it is covered
by vestiges of trophoblastic layer and the decidual cells of the
fused decidua capsularis and parietalis which can be
distinguished microscopically

10. fetal membranes contd.
 AMNION: It is the inner layer of the fetal membranes. Its
internal surface is smooth and shiny and is in contact with
liquor amnii.The outer surface consists of a layer of
connective tissue and is apposed to the similar tissue on the
inner aspect of the chorion from which it can be peeled off.
The amnion can also be peeled off from the fetal surface
of the placenta except at the insertion of the umbilical
cord.

11. FUNCTIONS
 Functions: (1) Contribute to the formation of liquor amnii
(2) Intact membranes prevent ascending uterine
 infection (3) Facilitate dilatation of the cervix during labor
(4) Has got enzymatic activities for steroid hormonal
 metabolism (5) Rich source of glycerophospholipids
containing arachidonic acid — precursor of prostaglandin
 E2 and F2á.

12. AMNIOTIC FLUID
ORIGIN: The precise origin of the liquor amnii still not well
understood. It is probably of mixed maternal and fetal origin.
From the very beginning of the formation of the extracoelomal
cavity amniotic fluid [AF] can be detected. This firstly water-
like fluid originates from the maternal plasma, and passes
through the fetal membranes by osmotic and hydrostatic
forces. As the placental and fetal vessels develop, the fluid
passes through the fetal tissue, as the exsudatum of the skin.
After the 20th-25th week of pregnancy when the
keratinization of skin occurs, the quantity of amniotic fluid
begins to depend on the factors that comprise the circulation
of AF.

13.  CIRCULATION: The water in the amniotic fluid is
completely changed and replaced in every 3 hours as
shown by the clearance of radioactive sodium injected
directly into the amniotic cavity. The presence of
lanugo and epithelial scales in the meconium shows
that the fluid is swallowed by the fetus and some of it
passes from the gut into the fetal plasma (vide
scheme).

14.  Amniotic fluid, volume is related to gestational age. It
measures about 50 mL at 12 weeks, 400 mL at 20 weeks and
reaches its peak of 1 liter at 36–38 weeks. Thereafter the
amount diminishes, till at term it measures about 600–
800 mL. As the pregnancy continues post term, further
reduction occurs to the extent of about 200 mL at 43 weeks,
due to placental aging and calcification.

15.  PHYSICAL FEATURES: The fluid is faintly alkaline with low
specific gravity of 1.010. It becomes highly hypotonic to
maternal serum at term pregnancy. An osmolarity of 250
mOsmol/L is suggestive of fetal maturity. The amniotic
fluid’s osmolality falls with advancing gestation.
 Color: In early pregnancy, it is colorless but near term it
becomes pale straw colored due to the presence of exfoliated
lanugo and epidermal cells from the fetal skin. It may look
turbid due to the presence of vernix caseosa.
 Abnormal color: Deviation of the normal color of the liquor
has got clinical significance.

16. Abnormal color ctnd
 — Meconium stained (green) is suggestive of fetal distress
in presentations other than the breech or transverse.
 Depending upon the degree and duration of the distress, it
may be thin or thick or pea souped (thick with flakes).
 Thick with presence of flakes suggests chronic fetal distress.
 — Golden color in Rh incompatibility is due to excessive
hemolysis of the fetal RBC and production of excess
bilirubin.
 — Greenish yellow (saffron) in post maturity.
 — Dark colored in concealed accidental hemorrhage is due
to contamination of blood.
 — Dark brown (tobacco juice) amniotic fluid is found in
IUFD. The dark color is due to frequent presence of old HbA.

17. COMPOSITION
In the first half of pregnancy, the composition of the fluid is
almost identical to a transudate of plasma. But in late
pregnancy, the composition is altered mainly due to
contamination of fetal urinary metabolites. The composition
includes—(1) water 98–99% and (2) solid (1–2%). The
following are the
 solid constituents:
 (a) Organic:
 Protein–0.3 mg% NPN–30 mg% Total lipids–50 mg%
 Glucose–20 mg% Uric acid–4 mg% Hormones (Prolactin,
insulin and renin)
 Urea–30 mg% Creatinine–2 mg%

18.  (b) Inorganic — The concentration of the sodium, chloride
and potassium is almost the same as that found in maternal
blood. As pregnancy advances, there may be slight fall in the
sodium and chloride concentration probably due to dilution
by hypotonic fetal urine, whereas the potassium
concentration remains unaltered.
NB:Lanugo grows on fetuses as a normal part of gestation, but
is usually shed and replaced by vellus hair at about 33 to 36
weeks, presence of lanugo in newborns is a sign of ……………..?
 (c) Suspended particles include—Lanugo, exfoliated
squamous epithelial cells from the fetal skin, vernix caseosa,
cast off amniotic cells and cells from the respiratory tract,
urinary bladder and vagina of the fetus.

19. FUNCTIONS
Its main function is to protect the fetus.
 During pregnancy: (1) It acts as a shock absorber, protecting
the fetus from possible extraneous injury. (2) Maintains an
even temperature. (3) The fluid distends the amniotic sac
and thereby allows for growth and free movement of the
fetus and prevents adhesion between the fetal parts and
amniotic sac.
 (4) Its nutritive value is negligible because of small amount
of protein and salt content, however, water supply to the
fetus is quite adequate.

20. FUNCTIONS CTND
 During labor: (1) The amnion and chorion are
combined to form a hydrostatic wedge which helps in
dilatation of the cervix. (2) During uterine
contraction, it prevents marked interference with the
placental circulation so long as the membranes remain
intact. (3) It flushes the birth canal at the end of first
stage of labor and by its aseptic and bactericidal action
protects the fetus and prevents ascending infection to
the uterine cavity.

21. Abnormalities
 AFI normal range 8-24 cm
Polyhydramnios AFI more than 25, Malpresentations, cord
prolapse, nuchal cord, true and false knots of cord,
Oligohydramnios AFI less than 8 more than 5
Severe oligohydramnios AFI less than 5.
Fetuses with too little amniotic fluid can develop contractures
of the limbs, clubbing of the feet and hands, and also develop
a life threatening condition called hypoplastic lungs. Baby
born with hypoplastic lungs, which are small
underdeveloped lungs, is potentially fatal and the baby can
die shortly after birth.

22. THANK YOU REMEMBER TO VOTE YOUR VERY OWN
DANNY WE CAN MAKE IT.
Reference
Duta’s textbook of obstetrics 7th edition revised
Williams Obstetrics 24th edition