The document summarizes the structure, function and abnormalities of the placenta and amniotic fluid. Some key points: - The placenta develops from fetal and maternal tissues and is complete by 12 weeks. It has both fetal and maternal surfaces separated by the intervillous space filled with maternal blood. - It functions to transfer gases, nutrients, and waste between mother and fetus through complex mechanisms like diffusion, transporters and barriers. - Abnormalities can include extra lobes (succenturiate placenta) or a thin membranous structure (membranous placenta) which can increase risks for the pregnancy. - Amniotic fluid originates from fetal urine

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

2. Placenta
• 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

3. Human placenta is
• Discoid in shape
• Haemochorial
• Deciduate

4. Placenta at Term- Gross Anatomy
• 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
• 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
• 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

7. • 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
• 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

9. • 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

10. • 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

11. • 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

12. 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

13. 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
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
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
• 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
• 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
• 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
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
• 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
• 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
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
chorionic laeve

25. 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
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

27. 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

28. 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
• 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
• 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. • 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

34. 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

35. 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

36. 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
• 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
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

39. 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
• 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
• 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

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

45. • Types
• Acute- sudden increase
• Chronic- gradual increase

46. • 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
Maternal
During pregnancy-
 Incresed incidence of preeclampsia
 Malpresentation
 Premature rupture of membranes
 Preterm labour
 Abruptio placentae
 Cardiorespiratory embrassment

48. 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
• 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
• 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. • Diagnosis
• FH<POG
• The uterus is full of fetus because of
scanty liquor
• Malpresentation is common

52. • 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