Cordocentesis
Introduction:
Cordocentesis, also referred to as Percutaneous Umbilical Cord Blood Sampling
(PUBS) test, is a prenatal diagnostic test that can be used to determine whether
there are any abnormalities present in a fetus. It consists of taking a sample of the
fetus’s blood from the umbilical cord for further testing.
Fetal and maternal blood supplies are typically connected in utero with one vein
and two arteries to the fetus.
The umbilical vein is responsible for delivering oxygen rich blood to the fetus from
the mother; the umbilical arteries are responsible for removing oxygen poor
blood from the fetus.
Definition:
Percutaneous umbilical cord blood sampling (PUBS), also called cordocentesis,
fetal blood sampling, or umbilical vein sampling is a diagnostic genetic test that
examines blood from the fetal umbilical cord to detect fetal abnormalities.
PUBS provide a means of rapid chromosome analysis and are useful when
information cannot be obtained through amniocentesis, chorionic villus sampling,
or ultrasound.
Purpose:
Cordocentesis may perform to help diagnosis any of the following concerns:
Malformations of the fetus.
Fetal infection (toxoplasmosis)
Fetal platelet count.
Fetal anemia and isoummunization.
Cordocentesis is usually done when diagnostic information cannot be
obtained through an amniocentesis CVS, ultrasound.
Indications:
Rapid Karyotype.
Hemolytic Disease
Severe growth retardation
Congenital infection
Contraindications:
Under the age of 18 weeks old
Mothers affected by hepatitis B
HIV positive mother ( if the fetus has been infected with HIV it may not be
contraindicated)
Risks:
Cordocentesis carries potentially serious risks, including:
Fetal bleeding: Bleeding from the area where the needle is inserted is the
most common complication. If life-threatening fetal bleeding occurs, your
health care provider might recommend replacement of blood products to
the fetus.
Cord hematoma: A collection of fetal blood within the cord might occur
during or after a cordocentesis. Most babies don't have signs or symptoms
when this occurs. However, a few might develop a low heart rate for a
short period.
- If the hematoma is stable, your health care provider will observe the
baby.
- If the hematoma isn't stable or if your baby's heart rate doesn't recover,
your health care provider will recommend an emergency cesarean
delivery.
Slowing of the baby's heart rate: The baby's heart rate might slow
temporarily after cordocentesis.
Infection: Rarely, cordocentesis can lead to a uterine or fetal infection.
Fetal-maternal bleeding: Fetal blood might enter maternal circulation in
about 40 percent of procedures. The amount of bleeding is usually small.
This problem is more common when the placenta lies in the front of the
uterus.
Passing maternal infection: If the mother has certain infections, such as
hepatitis B, hepatitis C or HIV, they might be passed to the baby.
Pregnancy loss: Cordocentesis carries a higher risk of fetal death than do
other prenatal diagnostic tests, such as chorionic villus sampling and
amniocentesis. The risk is about 1 to 2 percent for a fetus that appears
normal and is being tested for genetic disorders.
However, since many babies are ill when the test is done, it's often difficult
to determine whether fetal death is related to the procedure or to the
baby's health.
Note: Ultimately, the decision to have cordocentesis is up to you. Your health care
provider and a genetic professional can help you weigh the risks and benefits.
Procedure:
Before week 23 of pregnancy, cordocentesis is usually done in an
outpatient facility or the health care provider's office.
After week 23 of pregnancy, cordocentesis is usually done in the hospital, in
case the baby develops complications that might require an emergency
delivery.
A sample of mother's blood will be taken before the procedure for
comparison with the fetal blood samples.
Before procedure:
If you are 23 or more weeks pregnant, you'll be asked to avoid eating or
drinking after midnight the night before cordocentesis. This is because
certain complications caused by the procedure might require an emergency
cesarean section.
About 30 to 60 minutes before the procedure, you might be given
antibiotics to reduce the risk of a uterine infection.
If movement of the fetus is a risk to the success of the procedure, the fetus
may be paralyzed using a fetal paralytic drug.
During procedure:
Health care provider will use ultrasound to determine the umbilical cord's
location in uterus.
Lie women on her back on an exam table, and apply a special gel to her
belly. Then use a small device known as an ultrasound transducer to show
her baby's position on a monitor.
Sometimes medication is given to prevent discomfort during the procedure,
but often it isn't needed.
Guided by ultrasound, health care provider will insert a thin, hollow needle
(25gauze and 13cm in long) through abdominal and uterine wall to the
umbilical cord
Blood sampling may be achieved with more ease if the placenta is in the
anterior position. However, if the placenta is in the posterior position, the
fetus might block direct access to the umbilical cord.
Once the umbilical cord is reached and the correct position of the needle is
confirmed, the fetal blood is drawn.
The needle is removed after all necessary samples are taken. Generally 0.5
to/ml of fetal blood is collected.
The sample is sent to the laboratory for analysis and result.
After procedure:
The site of puncture is monitored after the procedure for bleeding.
If the blood sample was obtained at the site close to the placenta, a fetal
blood confirmation test should be done to ensure no mixing of fetal and
maternal blood occurred before the diagnostic tests are done on the blood.
Anti - immunoglobulin 100 µg (500 i.u) IM should be given to RH negative if
unimmunized women.
External fetal monitoring is done for 1 to 2 hours after the procedure.
Instruct the woman in fetal movement counts and to obtain result in 48 to
72 hours.
Results:
Health care provider or a genetic professional will help to understand
the results of cordocentesis.
If test results are normal, health care provider will discuss the need for
any follow-up appointments.
If baby has an infection, health care provider will explain the treatment
options. If your baby has severe anemia, he or she might need a blood
transfusion through the umbilical cord.
If test results indicate that baby has a condition that can't be treated,
woman might be faced with wrenching decisions — such as whether to
continue the pregnancy. Seek support from your health care team, your
loved ones and other close contacts during this difficult time.
References
Dutta, DC., (2018). Text Book of Obstetrics Including Perinatology and
Contraception, 9th edition, Jaypee Brother Medical Publisher (P) Ltd.
4838, 24 , Ansari Road , Daryagunj, New Delhi 1100002, India, Page no.
105-106
Subedi, D., Gautam, S., (2010). Midwifery Nursing II, 1 st edition, Medhavi
Publication, Baneshwor, Kathmandu, Nepal, Page no. 207
Tuitui, R., (2012). Manual of Midwifery I, 8th edition, Vidyarthi Pustak
Bhandar, Bhotahity, Kathmandu, Page no. 207
https://en.m.wikipedia.org/wiki/Percutaneous_umbilical_cord_blood
sampling
https://www.glowm.com/section-view/heading/Cordocentesis/item/212#
https://www.verywellfamily.com/cordocentesis-4175008
https://www.mayoclinic.org/tests-procedures/percutaneous-umbilical
blood-sampling/about/pac-20393638
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