It talks about the placental formation and structure and the amniotic fluid

1. Placenta and Amniotic fluid-
Structure, Function, and
Abnormalities

2. Placenta
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Human placenta develops from two
sources
Fetal component- Chorionic frondosum
Maternal component- decidua basalis
Placental development begins at 6 weeks
and is completed by 12 th week

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Human placenta is
Discoid in shape
Haemochorial
Deciduate

4. Placenta at Term- Gross Anatomy
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Fleshy
Weight-500gm
Diameter- 15-20 cm
Thickness-2.5 cm
Spongy to feel
Occupies 30% of the uterine wall
Two surfaces- Maternal and fetal
4/5th of the placenta is of fetal origin and 1/5 is
of maternal origin

5. Fetal surface of the placenta
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Covered by smooth and
glistening amnion
overlying the chorion
Umbilical cord is
attached at or near its
centre
Branches of the umbilical
vessels are visible
beneath the amnion as
they radiate from the
insertion of the cord

6. Maternal surface of the placenta
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Rough and spongy
Maternal blood gives
it dull red colour
Remanants of the
decidua basalis gives
it shaggy appearance
Divided into 15-20
cotyledons by the
septa

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Margins of the placenta are formed by fused chorionic
and the basal plate
Placenta is attached to the upper part of the uterine
body either at the posterior or anterior wall
After delivery ,placenta separates with the line of
separation being through decidua spongiosum
(intermediate spongy layer of the decidua basalis

8. Structure of the placenta
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Placenta is limited by the
amniotic membrane on
the fetal side and by the
basal plate on the
maternal
Between these two lies
the intervillous space
filled with maternal blood
and stem villi with their
branches

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Amniotic membrane-
single layer of cubical
epithelium loosely attached to
adjacent chorionic plate and
does not take part in placental
formation
Chorionic plate- forms the
roof of the placenta
From outside inwards consists
of
Syncitotrophoblast
Cytotrophoblast
Extraembryonic mesoderm
with branches of umbilical
vessels

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Basal Plate- forms the
floor From outside
inwards it consist of
Compact and spongy
layer of decidua basalis
Layer of Nitabuch
Cytotrophoblastic shell
Syncytiotrophoblast
Basal plate is perforated by
the spiral arteries allowing
entry of maternal blood into
intervillous space

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Layer of Nitabuch - is a fibrinous layer formed
at the junction of cytotrohoblastic shell with
decidua due to fibrinoid degeneration of
syncitotrohoblast
It prevents excessive penetration of the decidua
by the trophoblast
Nitabuch membrane is absent in placenta
accreta and other morbidly adherent placentas

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Intervillous space:
Numerous branch villi
arising from the stem villi
project into this space
It is lined internally on all
sides by the
syncytiotrophoblast and
is filled with maternal
blood

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Stem (Anchoring villi )
Arise from the chorionic plate and
extend to the basal plate
Fetal cotyledon (60-100 ) – derived
from one major primary stem villus
and is the structural unit of
placenta
Maternal cotyledon (15-20 )
contains 3-5 fetal cotyledons
Villus is the functional unit of
placenta
Total surface of the villi for
exchange varies between 4-14 sq
meters

14. Placental barrier or membrane
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Maternal and fetal blood
are separated by
placental membrane
or barrier (0.025 mm
thick )
Endothelial lining of fetal
vessels
Connective tissue of the
villi
Basement membrane
Cytotrophoblast
Syncytiotrophoblast

15. Placental Function
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Transfer of gases ,nutrients and waste
products , namely
Respiratory function
Nutritive function
Excretory function
Endocrine and enzymatic function
Barrier function
Immulogical function

16. Factors affecting the transfer
between mother and the fetus
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Physical properties of the substance- molecular
weight, lipid solubility, ionised substances
Area and functional integrity of the placental
membrane
Rate of blood flow
Concentration gradient of the substance on
either side of the exchange membrane

17. Mechanism involved in the transfer
of substances
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Simple diffusion-O2 and CO2
Facilitated diffusion ( carrier mediated ) –glucose ,
vitamins
Active transfer ( against concentration gradient )-ions
Endocytosis- invagination of cell membrane to form
intracellular vesicle
Endocytosis-Release of substances in the vesicles to
extracellular space eg IgG immunoglobulin

18. Respiratory function
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Although fetal respiratory movement occurs, no
active exchange of gases takes place
Intake of oxygen and output of carbon dioxide
take place by simple diffusion across the fetal
membrane
O2 delivery to the fetus is at the rate of 8 ml/kg
which is achieved by cord blood flow of 160
-320ml/min

19. Excretory function
• Waste products from the fetus such as
urea, uric acid, cretinine are excreted to
the maternal blood by simple diffusion

20. Nutritive function
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Fetus obtains its nutrients from the maternal blood
Glucose- transferred to the fetus by facilitated diffusion
Lipids for fetal growth and development has dual origin. They are
transferred across the fetal membrane or synthesised in the fetus
Amino acids are transferred by active transport
Water and electrolytes- Na, K ,Cl cross by simple diffusion, Ca , P,
and Fe cross by active transport
Water soluble vitamins are transferred by active transport but the
fat soluble vitamins are transferred slowly

21. Barrier Function
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Placental membrane is thought to be a protective barrier for the
fetus against harmful agents in the maternal blood
Substances with large molecular weight or size like insulin or
heparin are transferred minimally
Only IgG ( not IgA or Ig M )antibodies and antigens can cross the
placental barrier
Most drugs can cross the placental barrier and some can be
teratogenic
Various viruses, bacteria, protozoa can cross the placenta and
affect the fetus in utero

22. Immunological function
• Inspite of foreign paternally inherited
antigens in the fetus and placenta, there is
no graft rejection due to immunological
protection provided by the placenta

23. Endocrine and Enzymatic function
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Placenta secretes various hormones – Protein
hormones like HCG, human placental lactogen,
pregnancy specific beta 1 glycoprotein,,pregnancy
associated plasma protein, steroidal hormones like
estrogen and progestrone
Enzymes secreted are diamine oxidase-which activates
the circulatory pressor amines,oxytocinase which
neutralizes oxytocin, phospholipase A2 which
synthesizes arachidonic acid

24. Placental abnormalities
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Placenta succenturiata
(3%)
One or more small lobe or
cotyledon of placenta may be
placed at a varying distance
from the main placental
margin
A leash of vessels connecting
the main to the small lobe
traverse through the
membranes
Accessory lobe is developed
from activated villi on the

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Clinical significance-
If succenturiate lobe is retained
following birth of placenta it may lead
to
PPH
Subinvolution
Uterine sepsis
Poly formation
Treatment- exploration of the uterus
and removal of the lobe

26. Circumvallate placenta
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Development-
Due to smaller chorionic
plate than the basal plate
The chorionic plate does
not extend into the
placenta margin
The amnion and chorion
are folded and rolled
back to form a ring
leaving a rim of
uncovered placental
tissue

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Morphology
Fetal surface has a central
depressed zone surrounded by
a usually complete thickened
white ring made up of double
fold of amnion and chorion
Branching vessels radiate from
the cord insertion upto ring
only
Area outside the ring is thicker,
elevated and rounded

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Clinical significance
There are more chances of –
Miscarriage
Hydrorrhoea gravidarum
Antepartum haemorrhage
Preterm delivery
Fetal growth restriction
Retained placenta or membrane

29. Placenta marginata
• A thin fibrous ring is present at the margin
of the chorionic plate where the fetal
vessels appear to terminate

30. Membranous placenta
• The whole of the chorion is covered by
functioning villi and thus placenta appears
as thin membranous structure on
ultrasonography

31. Chorioangioma
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Are the most common benign tumors of
the placenta and are hamartomas of
primitive chorionic mesenchyme
Small tumors may be asymptomatic but
large tumors may be associated with
hydroamnios and antepartum
haemorrhage

32. Amniotic fluid
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It is the fluid in the amniotic sac surrounding the fetus
Origin – both mother and fetus
Transudation from maternal circulation across the
placental surface and fetal membranes
Active secretion from amniotic epithelium
Transudation across surface of umbilical cord and fetal
placental circulation
Contribution from fetal urine
Tracheobronchial secretion
Transfer across fetal skin

33. •
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Volume- varies according to the
gestational age
Measures
12 weeks – 50 ml
20 weeks- 400 ml
36 weeks- 800ml-1 liter
At term - it reduces to apprx 700ml

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Composition-
Organic constituents
Proteins-0.3 mg/dl
Glucose- 20mg/dl
Urea- 30 mg/dl
Non protein nitrogen-30mg/dl
Uric acid – 4 mg/dl
Creatinine -2 mg/dl
Lipids- 50 mg/ dl
Hormones- insulin,prolactin, renin
Inorganic constituents- Na, K,Cl
Suspended particles- Lanugo,Desqamated fetal skin cells,vernix caseosa,
shedded amniotic cells, cells from thr respiratory tract,GIT,Genitourinary tract

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Physical features
Faintly alkaline
Low specific gravity-1.010
Becomes highly hypotonic to maternal
serum at term pregnancy
Osmolarity of 250 mOsmol/liter is
suggestive of fetal maturity

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Colour
In early pregnancy it is colourless
At term becomes pale straw coloured due
to preence of exfoliated lanugo and
epidermal cells from fetal skin

37. Abnormal appearance
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Greenish- due to presence of meconium
Golden yellow-due to presence of bilirubin resulting from
fetal cell hemolysis due to Rh incompatibility
Greenish yellow- in post maturity
Dark maroon/ blood stained – due to altered blood in
accidental haemorrhage
Prune juice/dark brown- in presence of retained dead
fetus

38. Functions of amniotic fluid
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During pregnancy
Act as a shock absorber to protect the fetus from external injury
Maintains the fetal temprature
Allows free movement and growth of fetus
Prevents adhesion formation between the fetal parts and the
amniotic sac
Has some nutritive value because of small amount of protein and
salt content

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During Labour
It forms hydrostatic wedge to help dilatation of cervix
During uterine contractions , the amniotic fluid in the
intact membranes prevents interference with placental
circulation
Provides pool for the fetus to excrete urine
Protect the fetus from the ascending infections by its
bactercidal action

40. Clinical importance
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Study of amniotic fluid helps in knowing the well being
and maturity of fetus
Intramniotic instillation of prostaglandins and hypertonic
saline can be used for induction of abortion
Artificial rupture of membranes to drain liquor is a
method of induction and augmentation of labour
Excess liquor (polyhydroamnios), less liquor known as
(oligohydroamnios ) can be estimated by ultrasound
measurement of amniotic fluid index (AFI )

41. Measurment of AF
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Measurement of AFI-
quantitative method of
measurement of
amniotic fluid by usg.
Single largest pocket is
measured in four
quadrants and added.
Normal range is 5-24 cm
Single deepest pocket
Normal range is 2-8 cm

42. Polyhydroamnios
• Defined as excess of amniotic fluid of
more than 2000ml or AFI> 25 cm or
SDP>8cm

43. Etiology
• Idiopathic- seen in 2/3rd of the cases
Fetal causes-
Anencephaly
spina bifida
Esophageal and duodenal atresia
Facial cleft and neck masses
Congenital diaphragmatic hernia
Fetal sacrococcygeal teratoma
Fetal infections
Hydrops fetalis
Multiple pregnancy

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Placental causes- choriangioma of the
placenta
Maternal causes- Diabetes, cardiac or
renal disease

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Types
Acute- sudden increase
Chronic- gradual increase

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Symptoms- breathlessness due to
mechnacial compression, edema of legs,
varicosities in legs,
Signs-Abdomen is markedly distended,
skin is tense,shiny fundal height >POG,

47. Complications
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Maternal
During pregnancy-
Incresed incidence of preeclampsia
Malpresentation
Premature rupture of membranes
Preterm labour
Abruptio placentae
Cardiorespiratory embrassment

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During labour
Premature rupture of membranes
Cord prolapse
Uterine inertia
PPH
Puerperium
Subinvolution
Puerperal sepsis
Fetal Complications
High perinatal mortality due to prematurity and congenital
malformations

49. Management
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Rule out fetal congenital anomalies
Bed rest
Amnioreduction- 1-1.5 liters of amniotic fluid is removed over 3
hours to relieve maternal distress
Indomethacin therapy- impairs lung fluid production,enhances
absorption of amniotic fluid, decreases fetal urine production,
increases fluid movement across fetal membranes
Dose – 1.5-3 mg/kg from 24-35 weeks for 2 weeks
S/E- premature closure of patent ductus arterious

50. Oligohydroamnios
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Amniotic fluid is less than 200 ml at term or AFI < 5 cm
OR SDP< 2 cm
Etiology
Fetal chromosomal anomalies
Intrauterine infections
Drugs- PG inhibitors, ACE inhibitors
Renal agenesis or obstruction of the urinary tract
IUGR associated with placental insufficency
Amnion nodosum-failure of secretion by the cells of the
amnion
Postmaturity

51. •
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Diagnosis
FH<POG
The uterus is full of fetus because of
scanty liquor
Malpresentation is common

52. •
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Complications
Fetal
Abortion
Adhesions due to intramniotic adhesions
Fetal pulmonary hypoplasia, cord compression
Maternal
Prolonged labour due to inertia
Increased operative interference due to
malpresentation