Cordocentesis is an invasive procedure in which a sample of the fetal blood is removed from the umbilical cord. It is used in addition to amniocentesis and ultrasound to detect blood disorders.
Blood disorders detected by cordocentesis include infections such as toxoplasmosis and rubella, rhesus iso-immunization, metabolic disorders, hemophilia, life threatening anemia as well as suspected growth retardation.
The advantage offered by cordocentesis, also known as umbilical vein sampling or percutaneous umbilical blood sampling (PUBS) is that results are available in a few days. But this comes at the cost of a slightly higher risk of miscarriage than amniocentesis.
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The test begins with an ultrasound to locate the area where the umbilical cordA flexible structure that connects the fetus to the placenta during pregnancy. It carries blood, oxygen, nourishment and waste to the placenta. It is first formed during the fifth week of pregnancy and contains the yolk sac and body stalk.
Visit our comprehensive glossary for more pregnancy terms and definitions. inserts into the placentaThe placenta is a large disk shaped membrane responsible for providing nourishment to the fetus during pregnancy. It consists of three parts, the fetal part made up from the chorion membrane surrounding the fetus, the maternal part, formed from the decidua basalis layer of the uterine lining, and the intervillous space between the two plates. It is connected to the fetus by the umbilical cord and consists of tissue from both the mother and the embryo.
Its function is complex. It has been described as a simple organ that combines the functions of a kidney-dialysis machine, heart and lung machine and intravenous drip. It consists of enormous numbers of blood vessel branches that permit the exchange of nutrition and oxygen, from the mother's bloodstream to the fetus and the removal of wastes to the mother to be excreted. The placenta's remarkable quality is that it does so without the blood of the mother mixing with that of the baby.
It also is responsible for the production of vital hormones including, estrogen, progesterone, and human chorionic gonadotropin. After birth, the placenta is delivered, and is sometimes referred to as the afterbirth.
Visit our comprehensive glossary for more pregnancy terms and definitions.. The mother's abdomen is cleaned and numbed with a local anestheticAn agent or process that removes the body's sensitivity to pain. Anesthetics are usually medically administered chemicals, although they include other forms such as hypnosis, or the body's own ability to cause numbness through shock.
Anesthetics can either be local, whereby only a portion of the body or an individual organ is desensitized or general, in which the entire body is desensitized, with the result the patient is often temporarily unconcious.
Visit our comprehensive glossary for more pregnancy terms and definitions.. A long thin hollow needle is inserted through the abdominal wall into the uterus and introduced into a blood vessel in the umbilical cord about half an inch (one centimeter) from the placenta. A small sample of the baby's blood is removed and sent to a laboratory for analysis. After the procedure the baby's heart rate will be monitored for several minutes. This procedure can also be used to administer drugs directly into the fetal bloodstream or for intrauterine blood transfusions in pregnancies affected by Rhesus incompatibility.
Cordocentesis is only performed if a fetal abnormality has already been detected by some other test, usually ultrasound. If the test is performed to confirm an abnormality you should seek counselling prior to receiving the test. The choice you will have to make will depend on the strength of your convictions and your moral, ethical or religious beliefs about terminating pregnancy. You should seek counselling and must ask your family to provide considerable support.
A specific radio analysis of certain proteins that are present in the blood of the fetus can be used to detect infection such as rubella, toxoplasmosis and the herpes virus.
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If Rhesus incompatibility is present in the pregnancy a direct assessment of the fetal hemoglobinA complex protein-iron compound which forms part of the red blood cells. Hemoglobin carry oxygen to the cells and return carbon dioxide to the lungs.
Concentration of hemoglobin is different for men and women, with levels of 14 - 18 g/dl and 12 - 16 g/dl respectively. It has a structure which consists of 2 chains one with 141 amino acids and the other with 146. Any alteration in the the chains of just one amino acid alters the hemoglobin properties and is associated with sickle cell anemia.
Visit our comprehensive glossary for more pregnancy terms and definitions. can be used to determine the severity of blood cell destruction. Using this information a decision can be made about the need for an intrauterine blood transfusion, which is also performed through the umbilical vein.
Should there be reason to suspect intrauterine growth retardation analysis of the fetal blood can reveal the ph level (the acidity or alkalinity) of the fetal blood as well as the blood's oxygen, carbon dioxide ad bicarbonate levels. The fetal blood can also reveal the plasma levels of glucose.
When performed by a skilled and experienced operator the risk of miscarriage is the same as that for amniocentesis and chorionic villus sampling: about 1% - 2% above the risk of spontaneous miscarriage. The procedure may increase the risk of immediate fetal distress initiate premature labor.
If you are planning on having cordocentesis it is important to make sure that the operator who will be performing the test is experienced in the test. You should ask the facility where the test is to be performed what their miscarriage rate is as a result of cordocentesis. Ask your doctor for advice before committing to the test.
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Cordocentesis cannot be performed until week eighteen since the fetal vein is too fragile to permit sampling. Once the blood is removed test results can be returned very quickly since there is no need to culture fetal cells as there is in amniocentesis. You can expect to receive the results from cordocentesis in about forty eight hours.
The results of the test are dependent on the reason for the test initially. Your doctor will advise you about the specific results of the test.
The actions taken upon receipt of a positive result are dependent on the initial reason for the cordocentesis. Should rhesus iso-immunization require it a blood transfusion will be performed, also through cordocentesis. If the test is used to detect a fetal infection then the appropriate treatment will be provided.
If cordocentesis has been performed to confirm a genetic abnormality the decision whether to terminate the pregnancy or giving birth to a child with a life-long condition can be a traumatic and difficult one. If you plan to terminate the pregnancy you will need both medical advice and emotional support from your family. No matter how strong your convictions, this is always a difficult and stressful decision to make. Counselling for both parents is recommended, and membership of a support group may prove beneficial.
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