(also referred to as
fluid test or AFT),
is a medical procedure used in prenatal diagnosis of
chromosomal abnormalities and fetal infections, in which
a small amount of amniotic fluid, which contains fetal
tissues, is extracted from the amnion or amniotic sac
surrounding a developing fetus, and the fetal DNA is
examined for genetic abnormalities.
Before the start of the procedure, a local anesthetic
can be given to the mother in order to relieve the pain
felt during the insertion of the needle used to withdraw
the fluid. After the local is in effect, a needle is
usually inserted through the mother's abdominal wall,
then through the wall of the uterus, and finally into
the amniotic sac. With the aid of ultrasound-guidance, a
physician punctures the sac in an area away from the
fetus and extracts approximately 20 ml of amniotic
fluid. After the amniotic fluid is extracted, the fetal
cells are separated from the sample.
cells are grown in a culture medium, then fixed and
stained. Under a microscope the chromosomes are examined
for abnormalities. The most common abnormalities
detected are Down syndrome (trisomy 21), Edwards
syndrome (trisomy 18), and Turner syndrome (monosomy X).
In regard to the fetus, the puncture heals and the
amniotic sac replenishes the liquid over the next 24–48
in pregnancy, used for diagnosis of chromosomal and
other fetal problems such as:
• Down syndrome (trisomy 21)
• Trisomy 13
• Trisomy 18
• Fragile X
• Rare, inherited metabolic disorders
• Neural tube defects (anencephaly and spina bifida) by
Later on, it also can be used to detect problems such
• Rh incompatibility
• Prediction of lung maturity
• Decompression of polyhydramnios
An emerging indication for amniocentesis is in the
management of preterm rupture of membranes where
measurement of certain amniotic fluid inflammatory
markers may be helpful. If amniotic fluid IL-6, a marker
of inflammation, is elevated, the fetus is at high risk
and delivery should be considered.
procedure is done when a baby that is still in the womb
suffers from severe anemia. Anemia is a lack of red
blood cells. When the baby's blood count falls too low,
a transfusion is needed. A transfusion means giving the
baby red blood cells from a donor.
There are two types of fetal blood transfusions:
• Intravascular transfusion (IVT)—done through the
mother’s abdomen into the fetus’ umbilical cord; more
• Intraperitoneal transfusion (IPT)—done through the
mother’s abdomen and uterus into the fetus’ abdomen;
usually only done if IVT is impossible to do because of
the position of the baby and the umbilical cord
Reasons for Procedure
blood transfusions are done because the baby in the womb
is suffering from severe anemia and could die without
this transfusion. Anemia can be caused by:
• Rh incompatibility —the mother and baby have a
different type of blood, and mother’s antibodies to
fetal blood cells lyse (destroy) fetal blood cells.
• Parvovirus B19 infection —a viral infection the mother
The goals of fetal blood transfusions are to:
• Prevent or treat fetal hydrops before delivery—Hydrops
is caused by severe anemia in the fetus. The fetus
develops heart failure. This leads to fluid collecting
in the skin, lungs, abdomen, or around the heart.
• Continue pregnancy so the baby can be born close to
complications for mother and fetus include:
• Need for cesarean section (C-section) due to fetal
distress after the procedure
• Premature labor
• Graft versus host disease in the fetus (a rare
condition in which the donor’s blood cells attack the
baby's blood cells)
• Abdominal bruising or soreness
• Bleeding, cramping, or leaking fluid from vagina
• Injury to the fetus
• Giving too much blood
• Fetal bleeding
• Causing your water to break
Be sure to discuss these risks with your doctor before
To see if the fetus has severe anemia or fetal hydrops,
the doctor may do these tests:
• Amniocentesis —a sample of amniotic fluid is taken
• Cordocentesis—a blood sample from the umbilical cord
• Ultrasound —a test that uses sound waves to examine
the internal organs
fetus has hydrops, the blood transfusion will be done
Before the transfusion, you may be given:
• Pain medicine
• Muscle relaxant through an injection or an IV
Local anesthesia—numbs a small area of your abdomen
Description of the Procedure
With IVT, the fetus will be paralyzed for a short time.
This is to allow access to fetal blood vessels and to
reduce injury to the fetus. During both IVT and IPT, the
doctor will monitor the fetus with an ultrasound scan.
The ultrasound will:
• Show the position of the fetus
• Guide the placement of the needle through the amniotic
sac and into the vessel in the umbilical cord
• Record the fetal heart rate
The doctor will insert a needle into your abdomen. Using
ultrasound, the doctor will make sure the needle is
placed correctly. The needle will go through your
abdomen and be inserted into the umbilical cord (IUT) or
into the fetal abdomen (IPT). Blood will be transfused
to the fetus.
Before the needle is removed, the doctor will take a
final blood sample. This is to determine the fetus'
blood level (called hematocrit). The doctor will find
out whether the transfusion was enough and when the next
one should be.
The transfusions may need to be repeated every 2-4 weeks
until your doctor decides that it is safe to deliver the
Will It Take?
A 10 ml IVT transfusion will take 1-2 minutes. Usually,
between 30-200 ml is transfused during a single
Will It Hurt?
You will feel pain and cramping where the doctor inserts
the needle. If you are close to delivering the baby or
if the procedure is long, the uterus will be sore.
This procedure is done in a hospital setting. You will
be able to go home after the transfusion. If
complications occur, you may need to have a C-section.
The doctor may give you:
• Antibiotics to prevent infection
• Medicine to prevent contractions or labor
Be sure to follow your doctor’s instructions.
Once your baby has finally delivered, the baby will need
to have follow-up blood tests. The doctor will closely
monitor the baby for:
• Liver damage
• Congestive heart failure
• Respiratory failure
• Other complications if the baby is premature