The amniotic fluid surrounding the fetus in the amniotic sac provides protection, maintains temperature, and acts as a cushion. Amniocentesis is a procedure where a small amount of amniotic fluid is removed between 16-20 weeks of pregnancy using ultrasound guidance. Analysis of amniotic fluid can detect chromosomal abnormalities, neural tube defects, lung maturity, and other conditions.

1. What is an amniotic fluid?
• The fluid surrounding the fetus in the amniotic
sac is Amniotic fluid. It is derived from
maternal plasma in early pregnancy.
• The fluid volume increases as the baby grows
in size.

2. Functions of the amniotic fluid
• 1. Provides protection to the fetus.
• 2. Provides an even temperature.
• 3. Acts as a cushion to external trauma.
• 4. Allows the free movement for fetal growth.

3. Advantages of amniotic fluid analysis
• 1. Detection of chromosomal abnormalities.
• 2. Direct measurement of specific enzyme.
• 3. To detect neural tube defects and lung
maturity.

4. Amniocentesis ( procedure )
• Amniocentesis or amniotic fluid analysis is the
procedure of removal of small amount of
amniotic fluid from amniotic sac.
• This is done between 16th and 20th week of
pregnancy.
• A needle is inserted into the amniotic sac and
30ml of the fluid is collected.
• An ultrasonograph guided amniocentesis is done
to avoid trauma to the fetus, abortion, infection
or respiratory problems.

5. This tissue culture helps to detect the
following:
• 1. The sex of the fetus.
• 2. Chromosomal disorders.
• 3. Inherited enzyme deficiency.
• 4. Rh positive typing.

6. Investigation using amniotic fluid
• Alpha fetoprotein
It is a glycoprotein produced by yolk sac in large
amounts in the first trimester and by fetal liver in
the second trimester during the intrauterine life.
• Pathology
Increase levels of alpha fetoprotein are seen in
open neural tube defects like anencephaly,
exomphalos and spina bifida. Increased levels are
also seen in Turners syndrome.

7. • Phospholipids
Dipalmitoyl lecithin and Phosphatidyl inositol
appears at 24th week of gestation. It acts as a
surfactant without which the lung collapses. Thus
the levels of surfactants help to detect fetal lung
maturity.
Bile pigments
An increase in bilirubin level helps to detect
hemolytic disease of the newborn.

8. • Alkaline phosphatase
An increase in the enzyme level helps in prenatal
detection of cystic fibrosis.
Tamm horsfall glycoprotein
This glycoprotein is derived from fetal kidney
which acts as an aid to assess renal function.