Amniotic puncture, flake test and umbilical cord sampling
Amniotic puncture or amniocentesisAmniotic puncture is a study aimed at detecting abnormalities of the central nervous system (spina bifida and anencephaly) and some forms of mental abnormalities such as Mongolism (Down's syndrome). The gender of the baby can also be determined. When a hereditary disease occurs in a family that is gender-bound, this can be an important fact.
What happens with amniotic fluid puncture?Under local anesthesia, a hollow needle is inserted through your abdominal wall into the womb, so that approximately 14 grams of the fluid in which the fetus is located can be sucked up. This fluid has been swallowed by the fetus and then removed by urinating or spitting it out. It contains many cells, coming from the skin and from other organs, that can provide much information about the condition of the fetus. The moisture is centrifuged so that the cells are separated from the moisture.
In the 1950s, when amniotic fluid puncture was first applied, mistakes were sometimes made. The needle sometimes damaged the tissues of the placenta resulting in miscarriage. Now that an ultrasound is possible, the location of the placenta is accurately determined in advance and the risk of damage to it is much less. However, the procedure is not entirely without risk. It is estimated that there 1 to 2% chance is on a miscarriage. In connection with this small but undeniable chance, amniotic puncture is only justified if there is more than an average chance that you are pregnant with an abnormal baby. You must also be aware of the consequences. If the examination shows that there is something wrong with your baby, you should in principle be prepared for an abortion if it can be clearly stated that the abnormality is serious.
In the Netherlands, every woman who is older will have the opportunity to have this study done for 37 years, because the deviations that occur are more frequent the older the woman is. When a serious deviation is suspected, both parents are entitled to good information and consultation. They are facing a difficult time. Amniotic puncture can only be done between the 14th and 16th week of pregnancy. That makes it more difficult to decide, because if the suspicion turns out to be correct, abortion can only happen at a time that is actually too late. The woman affected by this experience is entitled to every conceivable support from her partner and her family.
The flake testThe flake test, the collection of chorion flakes, involves taking a sample of the tissue from the part of the outer membrane around the embryo (which will later become the placenta), to determine whether the fetus will have a hereditary handicap . One of the deviations that the test cannot detect is spina bifida, the 'open back'. The big advantage of the flake test over the amniotic fluid puncture is that the test can be done before the twelfth week. Sometimes even after six weeks from conception, so that an abnormality in the fetus can be detected much earlier and that the test is carried out through the vagina instead of through the abdominal wall.
However, the flake test is still in the testing stage and many questions still need to be answered before this test becomes the general practice. The tests are designed to discover whether the flake test is sufficiently accurate for routine use, and whether there are risks that outweigh the benefits, such as the frequent occurrence of infections or bleeding, or a spontaneous abortion (miscarriage) that follows the flake test. If you are asked to participate in a pilot study with the flake test, which compares this technique with the amniotic fluid puncture, it may be useful to do this. We do not yet know enough about both tests to say with certainty which one is the best.
A sample from the umbilical cordAt the end of the 1970s, fetoscopy, photographing the baby in the womb, was the latest technique for discovering what happened to babies who were known to be at risk. Doctors gave the woman an analgesic, introduced a narrow telescope through her abdominal wall and uterus and photographed the fetus in this way. Unfortunately, the risk of miscarriage with this method was found 5 to 10%.
Fetoscopy has now been replaced by taking a blood sample from the umbilical cord. This technique is welcomed by Dr. Stuart Weiner of the University of Pennsylvania as a technique that has opened up a whole new field of fetal medicine. When some blood is drawn from the umbilical cord, a very thin needle is inserted through the abdominal wall and uterus into the fetal vein of the umbilical cord, and a small amount of blood is withdrawn from the baby for testing.
Blood transfusions within the womb are also given in this way, and medication can be given directly to the baby with an injection. Because the fetal vein is tender during the first period of pregnancy, the technique cannot be performed before the eighteenth week.
Although still as an experiment, blood is taken from the umbilical cord in some research centers to supplement amniotic fluid puncture and ultrasound when the results are unclear. The method is also used if there is one sinus disease is to haemophilia in the baby, or to examine the baby for metabolism disorders. Dr. Kytros Nicolaides of King's College Hospital in London estimates that if the method is used by experienced doctors, the chance of losing a baby is only 1 percent. The size of the amniotic fluid puncture and the chorion flakes test in that hospital.