Umbilical cord puncture is an invasive examination method in prenatal diagnostics. In this procedure, a small amount of blood is taken from the umbilical cord of the unborn child. It is used to detect diseases and genetic defects in the child.
What is umbilical cord puncture?
Umbilical cord puncture is a procedure in which a small amount of blood is taken from the umbilical cord of the unborn child. It is used to detect diseases and genetic defects in the child. After the blood is collected through the umbilical cord puncture (chordocentesis), it can be tested for blood group incompatibility with the mother, metabolic disorders, toxoplasmosis or rubella. Toxoplasmosis is a feline disease that is normally completely harmless to humans, but is transmissible to humans (zoonosis). Only if the mother falls ill for the first time in the first trimester of pregnancy, the unborn child can be seriously damaged. If the mother was already ill earlier or if the infection occurs later, this is not dangerous for the unborn child. In addition, the blood can be searched for hereditary diseases and chromosomal abnormalities. If anemia is present, the unborn child can receive a blood transfusion through the umbilical cord. Umbilical cord puncture is also used to administer medications for infectious diseases. It is not possible to cure hereditary diseases or chromosomal abnormalities.
Function, effect, and goals
At the beginning of the umbilical cord puncture, the doctor uses an ultrasound machine to determine the exact location of the baby. Then he looks for an easily accessible site of the umbilical cord. This should be close to the placenta. A very thin needle is inserted into the umbilical cord through the mother’s abdominal wall and one to two mm of blood is taken. This examination is completely painless for the baby. The mother does not normally need to be anesthetized for this either. The umbilical cord puncture can be performed from the 18th week of pregnancy. This examination is recommended if the mother has abnormal blood values, previous ultrasound examinations have produced abnormal findings or to confirm the results of an amniocentesis, a chorionic villus sampling (examination of the placenta) or an associated FISH test. Chromosomal abnormalities that can be detected by this test are Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), Pätau syndrome (trisomy 13), or Klinefelder syndrome. Edwards and Pätau syndromes lead to severe damage to the unborn child and an extremely short life expectancy. Klinefelder syndrome is a chromosomal abnormality that occurs only in male babies. Their chromosome set has one or more extra x chromosomes. Males affected by this chromosomal abnormality are very feminine in appearance and are usually infertile. This chromosomal abnormality has no further effects. Due to the risk of complications, cordocentesis should not be performed without a compelling reason. Depending on what exactly is to be examined, the result of the examination is available after a few hours or within a few days. Determining genetic abnormalities takes longer than determining infection or anemia.
Risks, side effects, and hazards
The most common side effect of cordocentesis is contraction of the uterus. It feels like abdominal pain. In most cases, however, it is harmless and subsides relatively quickly. Infection can occur due to the penetration of the needle. Weak bleeding from the uterus and the discharge of amniotic fluid are also possible. Likewise, the uterus or placenta may be injured. If the baby moves unexpectedly during the examination, it can easily be injured by the puncture needle. Therefore, constant monitoring with the help of ultrasound is essential during the examination. The most serious complication that can occur is miscarriage. The risk is between 1% and 3% and depends on both the skill and experience of the physician and the age of the mother. If the unborn child is given a blood transfusion through the puncture needle, this can lead to a so-called umbilical cord tamponade. In this case, the blood is not introduced into the umbilical cord, but into the surrounding tissue.In this case, the child must be born immediately by cesarean section, as there is a risk of undersupply. The puncture can also cause blood from the unborn child to enter the mother’s bloodstream. In most cases, this is unproblematic. Only in the case of blood group incompatibility between mother and child does this become dangerous, because the mother’s bloodstream begins to form antibodies against the child’s blood. These antibodies can cross the placental barrier relatively easily. In the bloodstream of the unborn child, they would cause considerable problems and, in extreme cases, lead to permanent malformations or death. Therefore, in such a case, the mother is administered a drug as a preventive measure. Due to the relatively high risk of miscarriage and the possibility of further complications, an umbilical cord puncture should only be performed if previous tests and examinations have revealed a reasonable suspicion of a disease of the unborn child or a chromosomal abnormality. In these cases, too, the benefit and the individual risk must be thoroughly clarified with the attending physician before the procedure. Especially if a chromosomal abnormality is suspected, it is important to discuss with the partner what should be done if the suspicion is confirmed. A cure is not possible in these cases. Depending on the type of trisomy, the child has a very limited life span after birth. Therefore, in these cases, the question arises whether abortion is in principle an option, and if so, in what cases? Special psychological counseling is provided for parents in this situation.
