What tests can be done with the amniotic fluid extracted by amniocentesis? Amniocentesis is most commonly used for prenatal diagnosis. After obtaining amniotic fluid, a chromosome culture is done to analyze the karyotype of the chromosomes, which simply means that the 46 chromosomes are lined up to see if there is an extra or missing chromosome, or if there are large segments of chromosomes that are duplicated, inserted, or inverted. This is the most common type of prenatal diagnosis or karyotyping done today. With the development of technology, amniotic fluid can also be used for genetic diagnosis, such as specific genetic diseases, such as thalassemia, which is not a problem with the entire chromosome, but rather a large segment of a chromosome that is missing. Therefore, amniocentesis can determine whether the fetus has thalassemia major. Amniotic fluid can also be used for gene chips. If there is an abnormal site on the gene chip, it may involve some specific chromosome microdeletion or microduplication syndrome. The incidence of such syndromes is not high and can diagnose some rare and more difficult to explain fetal appearance anomalies, or severe fetal developmental disorders or mental developmental disorders in children. The amniotic fluid can also detect the blood group in the amniotic fluid and is mainly used for research in Rh-negative fetal anemia. Some mothers have Rh-negative blood and fathers have positive blood, and the fetus may also have positive blood, and the mother will produce antibodies to attack the fetus’ red blood cells, resulting in severe fetal anemia. If the abnormality is detected early, it is possible to treat the fetus intrauterine. The way to find out is to determine the fetal blood type through the amniotic fluid, and on the other hand to do amniotic fluid bilirubin test to see how severe the fetal hemolytic anemia is and whether it needs intrauterine transfusion. The amniotic fluid can also be used to diagnose intrauterine infections, which are not common bacterial infections or colds, but specific infections such as rubella virus, cytomegalovirus, toxoplasmosis, etc. These infections usually do not have much sequelae in adults, but may cause severe mental retardation, malformations, and developmental delays in the fetus. Therefore, for unexplained fetal anomalies, amniotic fluid can be taken to test for intrauterine infections. Is amniocentesis available for prenatal paternity testing? Amniotic fluid, chorionic villus, and umbilical cord blood are the three types of specimens that can be used for paternity testing. Amniotic fluid is relatively safe, and paternity testing is done by STR, also known as Short Tandem Repeat Sequence, which looks for a match between the fetal DNA fragment and the couple’s DNA to determine the type of paternity. Can amniocentesis determine the sex of a fetus? Of course it can. However, fetal sex determination cannot be done without medical indications. There are many mothers who want to know whether they are carrying a boy or a girl for various reasons, but there must be a medical indication for gender determination. Hemophilia is a genetic disorder on the sex chromosomes and is generally more serious in boys, while girls may only become carriers and not develop the disease. There is also a disease called Duchenne muscular dystrophy, which is also related to gender. Therefore, it is necessary to do IVF by assisted conception, where the cells of the embryo are taken out for sex determination before the embryo is planted, and if it is a boy, it may not be transferred in, but a girl can. In conclusion, it is technically possible to use amniotic fluid to determine the sex of the fetus, but there is no medical indication that sex determination is legally prohibited. Can albinism be detected by amniocentesis? Basically, yes. Because the genetic locus of albinism has been identified, it can be diagnosed through testing after the amniotic fluid is taken. However, amniocentesis is rarely done for albinism because firstly, the incidence is very low and secondly, albinism is not a lethal problem. From a medical point of view, even if the diagnosis is made, there is no indication to give up the child, and intrauterine treatment is not available for albinism. The prenatal diagnosis of amniocentesis is to diagnose serious fatal or disabling conditions that can be corrected by induction of labor or intrauterine treatment, but albinism is not one of these conditions. Can I have an amniocentesis for a low placenta? This includes both cases of placenta praevia and placenta praevia. Generally, there is a time limit for amniocentesis, mostly between 17 and 23 weeks. It is true that some mothers have a smaller uterine volume and a lower placenta attachment at this gestational week. We need to see if there is any bleeding or low placental abruption before doing the amniocentesis, but if there are no such high-risk factors, it does not affect the operation. The amniocentesis is performed avoiding the placenta. In addition, the stimulation of the 21 against the uterus is also very low. However, if the patient has symptoms of miscarriage, or even bleeding or contractions, avoid amniocentesis to minimize additional stimulation. Can phenylketonuria be detected by amniocentesis? Phenylketonuria is not a lethal disease at this time, so it is not included in the prenatal diagnosis. Phenylketonuria is now usually detected by screening the blood of the newborn. Regardless of whether the child has a family history of the disease, the government requires every newborn to have a blood specimen taken to check thyroid function, phenylketonuria, and G6PD deficiency (commonly known as Sericobacteria), which is called neonatal metabolic disease screening and is done in every hospital in Guangzhou. After screening for phenylketonuria, the pediatric department can help the child transition smoothly to normal development through food guidance and advice. Therefore, we also do not do prenatal diagnosis for the disorder phenylketonuria. Does everyone need to have an amniocentesis? Who needs to do it? Of course not, amniocentesis is mainly for patients who need prenatal diagnosis, including those who are at high risk for Down’s syndrome, such as those who are over 35 years old and have reached a high risk of Down’s syndrome index of 1/300 from the single aspect of age, so it is recommended that every pregnant woman of advanced age have an amniocentesis. If the test index is more than 1/250, it is also a high risk and prenatal diagnosis is recommended. Then there is the prenatal diagnosis that is also recommended for women who have previously had a child with Down’s syndrome or malformation to get pregnant again. If the fetus is found to have a serious heart malformation, intestinal obstruction or urinary tract fluid through ultrasound during pregnancy, prenatal diagnosis is needed to rule out chromosomal abnormalities, and if these malformations are not combined with chromosomal abnormalities, there is a time for surgery to correct the child after birth. However, if the chromosomal abnormalities are combined with Down’s syndrome, even if the surgery is done, the child’s intelligence and other problems will be a financial burden to the society and the family. There are also some groups of people, such as those with familial hereditary disease thalassemia, where both husband and wife are carriers of the same type, who need to determine if the child is severely thalassemia and need to undergo amniocentesis. There are also cases where the mother is Rh-negative and the child is suspected to have Rh-inappropriate hemolysis, which requires amniocentesis. If intrauterine infection is suspected, such as small fetal growth, atypical malformations, or edema-like changes in the fetus, it is necessary to find out if the fetus has a specific viral infection, and a prenatal diagnosis such as a TORCH test is required. When is the best time to do amniocentesis? Amniocentesis is now the most used prenatal diagnostic method. Three types of specimens are available for prenatal diagnosis: chorionic villus, amniotic fluid, and cord blood. The characteristic of chorionic hair is that it can be known at an early stage. The time to do chorionic hair testing is 11-13 weeks +6 of pregnancy, but the risk is higher, as a part of the tissue is taken from the placenta for testing, and the risk of bleeding or miscarriage is up to 2%, which is relatively high. Another method is cord blood aspiration, which is suitable for pregnant women who are older and have missed the amniotic fluid and chorionic villus test, and can be done after 24 weeks of pregnancy. Of course, there are some specific tests that cannot be replaced by amniocentesis, such as knowing if the fetus is anemic and needs to have the baby’s blood drawn for laboratory tests, to be done by cord blood puncture. In summary, chorionic villus puncture is a risky procedure; cord blood puncture is a risky procedure because of the large gestational age and the delay in termination of pregnancy once the fetus is found to be abnormal, so these two methods are not used particularly often. Therefore, the most used method is amniocentesis, which is performed between 17 and 23 weeks. Is it better to do amniocentesis or cord blood puncture at 24 weeks of pregnancy? Objectively speaking, the time to do amniocentesis is between 17-23 weeks of pregnancy, and amniocentesis is usually not done at 24 weeks. It is not that individual doctors do not do it, but because we take the amniotic fluid for testing to extract the cells shed from the fetal epidermis, and after 24 weeks, the fetal epidermal cells will be keratinized, and the success rate of the culture of these keratinized cells will be reduced, and the culture may not even come out in a month, so the test report will not be issued. Therefore, amniocentesis is not recommended after 24 weeks. As for why it cannot be done earlier, it is because the fetal amniotic fluid is limited before 17 weeks, if another 10 to 20 ml of amniotic fluid is drawn at this time, it will have a great impact on the fetus, plus there are fewer fetal shed cells before 17 weeks, so the best time is between 17 and 23 weeks. Are amniotic fluid test results reliable? Is it accurate? The principle of amniotic fluid test is cell culture. Don’t think that amniotic fluid is all water, in fact, once centrifuged, you can collect the shed cells for culture. Therefore, it takes 4-6 weeks for the results of amniocentesis to come out. The process of culturing the cells can also be affected by many factors that have an impact on the accuracy. Overgrowth can occur during the culture process, and the cells can develop abnormally after isolation. For this kind of amniotic fluid report results need to be very careful, will not look at a single cell karyotype judgment, a standard test to count 20 cells, each cell karyotype to count clearly, and even for suspected local a certain cell mass appears to differentiate abnormalities to count up to 50 cells karyotype, so the workload is also very large. Therefore, the results of amniocentesis are close to 99% or more reliable, but it is true that the process of amniotic fluid cell culture may be affected, resulting in cells not being cultured, abnormal cell division due to environmental influences, or even chimerism, partly normal and partly abnormal, requiring clinical analysis and, if necessary, even cord blood puncture to confirm the diagnosis. Is amniocentesis dangerous? What are the complications? Amniocentesis carries risks, and the main risk of amniocentesis is fetal loss. Part of this is due to the stimulation of the uterus by the puncture needle. After the puncture, the uterus contracts and bleeds, and the fetus is expelled naturally, called fetal loss. In fact, we choose a very fine puncture needle, thinner than the one used to draw blood. The larger the number, the thinner the needle. Generally, the needle used to draw blood is about 11, while the amniocentesis needle is 21 or 22. There is also a risk of bleeding. Sometimes the location chosen for the puncture crosses the placenta or crosses the rich blood flow in the uterine wall, which can easily lead to bleeding, but because the puncture needle is small, the blood in the wound will self-clot. There is also the risk of surgical infection. The chances of infection in a standard laboratory can be minimized by aseptic practice. In general, the risk of amniocentesis is usually less than 1%, and every effort is made to minimize the risk during the procedure, such as using the thinnest needle possible; using ultrasound guidance to see the position of the placenta and fetus and avoiding the placenta as much as possible during the puncture; and sometimes when the entire anterior uterine wall is covered with placenta and the placenta must be crossed to retrieve the amniotic fluid specimen, the surgeon will use surgical techniques to cross the placenta quickly to minimize bleeding. After amniocentesis, what treatment or other tests should be done next? After the amniocentesis, the doctor will explain some precautions, advise of possible complications and the need for monitoring. Most hospital stays after amniocentesis are not long and you can be discharged the same day or the next day at most. While staying in the hospital for observation, attention should be paid to any additional signs of labor or chances of miscarriage such as stomach pain, bleeding, and watering. It will also be advised not to do strenuous activities, heavy water lifting, or heavy physical labor for a week to avoid complications from the procedure. If the results of the amniocentesis are normal, the examination of the chromosomal aspects of the fetus is basically finished. However, chromosomal abnormalities are only part of the prenatal examination, and if the chromosomes are confirmed to be normal, screening for cosmetic abnormalities will be done as part of the routine maternity examination. In other words, after the amniotic fluid examination at 17 weeks, a 3-D ultrasound will be done at 22 weeks to rule out cosmetic abnormalities, not to say that if the chromosomes are fine, all other aspects are fine. So systematic maternity checkups are still needed. If the amniotic fluid report is abnormal, it depends on whether it is a true abnormality or a false abnormality. A true abnormality means that the report shows that the child has a chromosome that is triploid, and the doctor will recommend that the mother and family come in for a consultation to see if they want to give up the child. If the report shows that the child has thalassemia, the doctor will analyze with the pregnant woman and her family whether the child should be abandoned if the child has severe thalassemia, or if the child has mild thalassemia, what the child’s prognosis is and whether further follow-up is needed. This is why it is important to have a follow-up consultation after the amniocentesis. Another part of the case is a pseudo-abnormality, such as an unsuccessful amniotic fluid culture, and the doctor may suggest a different method for prenatal diagnosis. Sometimes there may be chimerism, where ten normal cells and ten abnormal cells are cultured. The prognosis for such children needs to be analyzed by the doctor as to whether the chimerism is true or false, and whether repeat amniocentesis is needed. There is no treatment for Down’s syndrome and it may be necessary to induce labor; however, some diseases such as Rh hemolytic anemia can be treated intrauterine by infusing foreign blood into the umbilical cord to combat the anemia, and there are many successful cases, but it may require a blood transfusion once a week or two. The child may not continue to be anemic after it is born free of maternal antibodies, so intrauterine treatment is possible once diagnosed, and patients are advised to do it because Rh hemolytic anemia is only aggravated in one fetus. It may be more serious in the next pregnancy if it is not done in this one. In case of intrauterine infection, there is no specific treatment and the prognosis of the child needs to be evaluated to make the decision to keep or induce labor. How is the amniocentesis procedure? Does it hurt? It is impossible to say that amniocentesis is completely painless, but there is no need to be too anxious. First of all, the needle chosen is very fine and if the pregnant woman can accept the stimulation of the needle used to draw blood, she can accept the stimulation of this puncture needle. Most mothers are more anxious because they are worried about the effect on their baby, so they will do psychological counseling before doing this test and slowly get used to it. Some mothers who are very anxious and nervous can have local anesthesia, where lidocaine is injected at the puncture site to reduce the mother’s pain. What should I pay attention to before the amniocentesis procedure? Before the procedure, we will check several things: firstly, whether there are indications for puncture, i.e. whether the mother is at high risk for Down’s syndrome; secondly, whether she has syphilis, HIV or hepatitis, which can be carried to the uterine cavity through puncture and cause secondary infections. Since hepatitis is more common nowadays, if amniocentesis is indicated, prophylactic immunoglobulin can be used before the puncture to counteract the chance of secondary intrauterine infections. For syphilis and AIDS, according to current industry and international practice, the possibility of interventional puncture should be reduced for AIDS and not performed during active syphilis. In addition, routine ultrasound is a must. Preoperatively, we can determine the position of the placenta, whether it will be hypoplastic, or whether most of the placenta is in the anterior uterine wall affecting the surgical view. Now many do prenatal diagnosis of twin fetuses, puncture is very important, most are two chorionic fetuses, need to take two specimens, where to enter the needle is very important, blind puncture may be twice inside the same amniotic cavity, and also involves puncture out the results of which child is problematic and need to reduce the fetus. What is the exact procedure of amniocentesis? The general process of amniocentesis is to make an appointment first, and the pregnant woman can have breakfast first when she comes at the appointed time. If there are contractions or bleeding, the baby cannot be punctured. If there are no contractions or bleeding, the baby’s condition will be checked by ultrasound, and the position of the placenta and fetus will be determined. The majority of pregnant women do not need anesthesia during the whole puncture process, and most of them do not need anesthesia, and some of them are very nervous and can be given local anesthesia with lidocaine. Disinfect the abdomen before anesthesia, lay a sterile towel to maintain relative sterility and minimize intrauterine infection, use a sterile probe ultrasound machine to see the baby’s position during the procedure, and the needle and probe operate simultaneously to ensure that how deep the needle can be seen, and try to enter the needle at once. After the needle is inserted, two milliliters of amniotic fluid is first withdrawn to ensure that the needle is in the amniotic pool and that the amniotic fluid is not contaminated with the mother’s blood, because the process of inserting the needle passes through the subcutaneous tissue and the needle tip carries the mother’s blood, so one to two milliliters of amniotic fluid is first withdrawn and discarded. The amount of amniotic fluid to be drawn next varies depending on the case. For karyotyping, about 20 ml of amniotic fluid is needed; for thalassemia, more than a dozen ml of amniotic fluid is needed. In general, around 17-23 weeks, the total amount of amniotic fluid is estimated to be 500-600 ml or more, and the extraction of a few tens of ml of amniotic fluid will not have a major impact on the entire amniotic pool. During the process of amniotic fluid extraction, the ultrasound machine is always running, observing whether the small child will move and whether the needle will be moved, and monitoring whether the fetal heart rate is normal in real time. After the needle is removed, there will be a needle hole on the belly and a band-aid will be applied. After 24 hours, the needle is basically closed and the band-aid can be removed. Amniocentesis is a minimally invasive test and the entire procedure takes about 5-10 minutes. After the puncture, you can get up and move around normally, but you cannot leave the hospital immediately. 1-2 hours after the puncture, you need to listen to the fetal heart by Doppler to make sure that the baby’s heartbeat is normal and that the pregnant woman has no contractions, so you can basically go home. I was afraid of low amniotic fluid and drank a lot of warm water before the test, does it have any effect on the test report? There is no direct relationship between the amount of amniotic fluid and the amount of water the mother drinks. The source of amniotic fluid production is mainly due to the surface osmosis of the fetal membranes and the urine produced by the fetal urinary system, so the amount of water the mother drinks cannot directly affect these factors. However, if the mother is in a state of extreme dehydration, it can also cause a lack of blood volume in the fetal circulation, resulting in low amniotic fluid, but this is very rare, so whether the mother drinks water or not does not affect the operation of amniocentesis or the results of the test report. What are the effects of amniocentesis on the fetus and will the fetus be hit when the needle is inserted to remove the amniotic fluid? The doctor will minimize the impact on the fetus and reduce the risk of fetal damage. The amniocentesis is performed in the thickest part of the amniotic fluid pool, avoiding the head and eyes of the fetus. Some small children are very active and we do not give the needle to keep the child asleep and still before the puncture. Sometimes we avoid the head of the fetus, but the child is smart enough to know that something has entered and will touch the puncture needle with his or her hands and feet. Do I need to be hospitalized for amniocentesis? What should I be aware of? Amniocentesis is usually done on the same day, or even in some cases on an outpatient basis, and you can leave after the procedure for observation. What are the conditions that require hospitalization after amniocentesis? Some pregnant women who have contractions after amniocentesis may need to be hospitalized. In addition, complications from amniocentesis are most likely to occur within a week after the puncture. We will explain to the pregnant woman that she will need to be hospitalized if she has contractions, stomach pain, bleeding, or premature rupture of membranes after returning home. What do I need to pay attention to after having an amniocentesis? Precautions: First, avoid wet water in the needle eye after amniocentesis for 24 hours to reduce infection; second, reduce strenuous exercise and avoid lifting heavy objects after going home; third, go to the hospital at any time if there are abnormalities.