The amniotic sac and fluid surround and protect the growing fetus during pregnancy. The sac develops around the 12th day of gestation and initially forms on the dorsal surface of the embryo, later surrounding the entire fetus except where it attaches to the umbilical cord. Amniotic fluid is produced from maternal and fetal sources and is constantly exchanged, with the entire volume turning over every 3 hours. The volume increases throughout pregnancy, reaching about 1000 ml by 36-38 weeks gestation. Examination of the amniotic fluid provides information about fetal health, maturity and complications of pregnancy.

1. AMNIOTIC SAC AND FLUID
KUMARI HITUMI
(M.Sc. Nursing , OBG)

2. AMNIOTIC SAC
• A Fluid filled sac/bag inside mother’s uterus
during pregnancy where the fetus develops
and grows.
• Also known as- Bag of water , Gestational sac,
amniotic cavity , fetal sac , membranes or fetal
membranes.

3. DEVELOPMENT
• On 12th post ovulatory day a fluid filled space
appers in between ectodermal layer and
cytotrophoblast is known as amniotic sac. Its
floor is of ectodermal origin and rest of the
wall is formed of primitive mesenchyme.
• Initially ,the cavity is located on the dorsal
surface of embrayonic disc.with formation of
head, tail and lateral folds ,it surrounds the
fetus.

4. DEVELOPMENT
• Fluid accumulation starts slowly in the sac and
ultimately the loose fluid filled cavity enlarges
enough to obliterate chorionic cavity.
• The liquor amnii surrounds the fetus
everywhere except at its attachment with the
body stalk.

5. FETAL SAC

6. ORIGIN
• Probably mixed maternal and fetal.

7. SOURCE AND CIRCULATION OF AMNIOTIC FLUID

8. CIRCULATION
• The fluid gets completely exchanged in every 3
hours.
• Presence of lanugo,epithilial scales in
meconium shows the fluid is swallowed by the
fetus.

9. VOLUME OF AMNIOTIC FLUID
• It varies as per gestational age.
• Its about 50 ml at 12 weeks.
• Its about 400 ml at 20 weeks.
• Its about 500 ml at 24 weeks.
• Its about 1000 ml at 36-38 weeks.
• Its about 600-800 ml at 40 weeks.

10. PHYSICAL FEATURES
• Fainty alkaline with low specific gravity 1.0010
• Highly hypotonic to maternal serum at term.
• Osmolarity of 250m osmol/L suggests fetal
maturity
• Osmolality falls with advancing gestational age.
• COLOR: Colorless initially and pale straw color at
term pregnancy.
• CLARITY:Turbid

11. ABNORMAL COLOR
• Deviation in normal color of liquor amnii has
clinical significance.
• Greenish apperance is suggestive of
meconium staining and fetal distress.higher
viscosity suggests chronic distress.
• Golden: In Rh incompatability is due to
excessive hemolysis of fetal RBC and
production of excessive bilirubin.
• Saffron (greenish yellow):In post maturity.

12. ABNORMAL COLOR
• Dark color: in concealed accidental
haemmorhage is due to blood contamination.
• Dark brown :IUD

13. COMPOSITION
• In firstly half of the pregnancy ,the composition of
amniotic fluid is almost identical to transudate of
plasma.
• In late pregnancy the composition gets contaminated
due to fetal urinary metabolites. It includes 98-99%
water and 1-2% solid.
• Solid constituents includes:
1.Organic
(protein 0.3mg%,glucose20mg%,urea30mg%uric acid
4mg%,creatinine2mg%,total lipids50mg%,non protein
nitrogen 30mg%,hormones:prolactin,insulin,renin ).

14. COMPOSITION
2. Inorganic:Na,CL,K.
3.Suspended particles:lanugo,squamous
epithelial cells of fetus,vernix
caseosa,amniotic cells.

15. FUNCTIONS
DURING PREGNANCY
• Protection of the fetus by acting as shock
absorber .
• Thermoregulation.
• Allows growth and free movement of fetus.
• Prevents adhesion of fetal parts and amniotic
sac.

16. FUNCTIONS
DURING LABOUR
• Amnion and chorion combines and helps in
cervix dilatation.
• During uterine contraction, it prevents
interference with placental circulation.
• It flushes the birth canal at the end of first
stage of labour and protects the fetus from
any kind of infection as it has antiseptic and
antibacterial action.

17. CLINICAL IMPORTANCE
• Fluid examination provides information of
fetal well being and maturity.
• Intra amniotic instillation of chemical is used
as a method to induce abortion.
• Rupture of membrane with liquor drainage is
helpful in induction of labour.