Can amniocentesis confirm mental retardation at 12 weeks of pregnancy

Amniocentesis confirms more accurate than Downs screening, there is also a FISH test that is optional when doing amniocentesis, this is a direct result without going through cell culture, which is even more accurate than amniocentesis, but add more than $2K. The optimal cycle for amniocentesis is 16-21 weeks, and if it's beyond that, your doctor will recommend a cordocentesis.　　Older pregnant women in general, the Down's syndrome screening will be due to the age of the proportion of the higher, but mainly to measure genetic diseases such as Down's syndrome, the current proportion of Down's syndrome than in previous years has increased substantially, but because of the high age of its proportion of the higher proportion of the judgment of the artificial proportion of the baby out of some of my friends insisted on not doing amniocentesis out of the baby is also very normal, but at present, in order to not be held liable for the hospital is generally required to sign your certainty do not do it before you can.　　Down syndrome, also known as congenital stupidity and trisomy 21, is the most common chromosomal disorder and cause of mental retardation, with a prevalence of about 1/700 or so in newborns. Depending on the chromosomal karyotype, Down syndrome is categorized into three types: simple trisomy 21, chimeric, and translocation. The development of Down syndrome originates from chromosome nondisjunction during meiosis occurring in the egg or spermatogenesis, which usually occurs randomly, with about 95% of nondisjunction originating from the mother and only about 5% occurring during spermatogenesis. The result is an extra chromosome 21, and the extra chromosome disrupts the balance between the genetic material of the normal genome due to the dosage effect, leading to mental retardation, craniofacial malformations and special facial features, hypotonia, and mostly complicated by congenital heart disease in the affected children, and the incidence of leukemia in the patients is 10-20 times higher than that in the general population. Life is difficult to take care of themselves, and the prognosis of patients is generally poor, with about 50% dying before the age of 5. Currently, there is a lack of effective treatment for Down syndrome.　　The age of the pregnant woman is closely related to the occurrence of Down syndrome, which is a genetic disease. Theoretically, when one of the spouses is trisomy 21, one of the children born will develop the disease. The majority of patients with Down syndrome with trisomy 21 alone are due to random gamete formation, have normal parents, have no family history of the disease, and are closely related to advanced age. Therefore, it is possible to carry a fetus with Down syndrome even if neither of the spouses is an individual with Down syndrome. Translocated patients are usually inherited from their parents. In the case of a parent with a balanced chromosomal translocation, 1/3 of the children born will be normal, 1/3 will be translocated, and 1/3 will be carriers of the balanced translocation. If one parent is a 21/21 balanced translocation carrier, 100% of their live births will be 21/21 translocation patients.　　Amniocentesis is performed for further testing. It is performed with a long needle with an inner diameter of about 0.6 millimeters, which is guided by ultrasound through the pregnant woman's abdomen, through the wall of the uterus, to the amniotic cavity, where 20 milliliters of amniotic fluid is withdrawn.　　Fetal cells in the amniotic fluid are cultured to analyze the chromosomes of the cells, as well as the activity of many enzymes, which can be used to detect chromosomal abnormalities, genetic abnormalities, or prenatal diagnosis of inborn metabolic abnormalities.　　It is usually performed at 15-20 weeks and no later than 22 weeks.　　Before 15 weeks, the amniotic fluid volume is low and the miscarriage rate of the puncture is high. after 22 weeks, the test is less successful as fewer cells are shed.　　So if it is a fetus between 22-24 weeks and a genetic diagnosis is desired, fetal umbilical vein puncture can be done.　　The main danger of amniocentesis, is water breakage. If the water breaks, it can cause a miscarriage. This happens about 3% of the time and cannot be completely avoided, even with the best technical experience.　　Some pregnant women worry that the puncture will insert the fetus. Since it is performed under ultrasound guidance, it will not injure the fetus and blandly will not cause fetal abnormalities.　　Amniocentesis is one of the prenatal diagnostic methods used to check for chromosomal abnormalities, neural tube malformations, and specific genetic disorders in order to prevent the delivery of a child with birth defects.　　Several factors are known to be more likely to result in fetal death, including the use of a larger-gauge needle during the puncture, multiple punctures, placental damage, and the appearance of abnormal coloration of the amniotic fluid. However, there are some reports that negate these causes, especially with regard to placental damage, and some reports suggest that the presence or absence of a puncture needle passing through the placenta does not affect the chances of fetal death. The general opinion at present is that if the placenta must be passed in order to extract amniotic fluid, the needle should always be inserted through the thinnest side of the placenta. With current technology, amniocentesis is a reasonably safe test.　　Water breakage: 1% incidence, will heal on its own within a few days.　　Amniocentesis: 0.1% incidence, causes lower abdominal pain, fever and other symptoms, and is highly susceptible to preterm labor.　　Vaginal bleeding: incidence 2-3%, will improve on its own within a few days.　　Fetal puncture: rarely occurs under ultrasound guidance. Occasionally, the fetus will move suddenly, which can be avoided immediately by the physician, and the puncture will heal on its own.　　Respiratory distress: A few studies have found that fetuses who have undergone amniocentesis are more likely to have respiratory distress after birth, with an incidence of 1.1%, compared to 0.5% for fetuses who have not undergone amniocentesis.　　The amniotic fluid test is mainly to check if the child has any chromosomal problems. There are generally 23 pairs of chromosomes, one autosomal and one sex chromosome.　　What kinds of chromosomes are recommended for amniotic fluid testing? One is the family has a genetic disease, like some hemophilia, or Mediterranean anemia, the family has this kind of hereditary disease, not that the child is 100% morbidity, there may be 50% or 25% morbidity rate of this kind of time, the child in the end there is no chromosomal problems through the amniotic fluid test to find out, one is a hereditary disease, and the other one, the previous she gave birth to a chromosomal abnormality of the child. If she has a history of fetal abnormality, we recommend that she do it.　　In addition, she is particularly old, like us over 35 years of age, pregnant women of advanced age, we also want to do, because this kind of people are often due to some harmful stimuli in the outside world after the chromosome segregation of the fertilized egg in the process of development, resulting in an extra chromosome, also appeared in the so-called trisomy chromosome, which is prone to cause malformations. Some of the more common trisomy of chromosomal abnormalities, such as trisomy 21 and 18 three days, 21 three days of our human chromosomes may be two, a father or mother's chromosomes are not separated, so that the child's 21 chromosomes there are three, so that the child appeared 21 trisomy after the performance of the congenital anomalies, in this regard, we are also very serious about this, this kind of child is born after the manifestation of intellectual disability, can not take care of themselves, to the child and the child, and the child can not take care of themselves. After birth, this kind of child will be mentally retarded and unable to take care of himself, which will affect both the child and the family. Therefore, we recommend amniocentesis to all pregnant women over 35 years old.　　What other types of pregnant women need to have amniotic fluid chromosome tests? We now do a trisomy 21 screening when the mom is 16 weeks to 18 weeks pregnant or earlier in some cases, which is Down's screening, or DS screening in English.　　Moderator: Does it actually serve the same purpose as Down's screening?　　Obstetrician and gynecologist Luo Lihua: This screening is through the mother's blood changes in hormone levels, such as AFP, ACG, E3, combined with the mother's age, gestational weeks, calculate a risk factor. If the risk coefficient is higher, we call it a high-risk group, she may have a higher chance of having a child with chromosomal abnormality, and we recommend chromosomal testing for this group.　　Moderator: This is a chromosomal test to rule out the high-risk group, and then an amniocentesis to rule out congenital stupidity.　　Obstetrician and gynecologist Luo Lihua: pumping the mother's amniotic fluid for culture is invasive to the mother, but the doctor will be in the ultrasound positioning to avoid the child to extract the amniotic fluid, but the puncture process is certainly through the mother's abdominal skin and the uterus, and sometimes a part of the people who may be through the puncture into the uterus after the uterus caused by uterine contractions, resulting in the possibility of miscarriage, after all, there is an invasive, so you can't be all the mothers for the sake of screening. So we can't do chromosome testing for all mothers in order to screen for chromosomal abnormalities, it's not realistic, so generally at 16 weeks we do screening through blood tests, and after screening out the high-risk group, this part of the population suggests that she go back to do it again.　　Moderator: Down's syndrome screening is not necessary for everyone, it depends on whether it is voluntary or involuntary, right?　　The expert in obstetrics and gynecology Luo Lihua: generally you tell her that certainly all do.　　What is amniocentesis: amniocentesis is the amniotic fluid produced in pregnancy through a simple instrument under sterile pumping out a number of milliliters to be impatient laboratory tests in order to determine the health of the fetus director of the recovery Wednesday this quality surgical guidance is best to carry out in the pregnancy ~ weeks too early amniotic fluid is not good enough for more than the difficulty of extracting the specimen in the heart is easy to all kinds of injuries to the fetus to go out of the clinic; too late the fetus Dane has been developed and shaped fortunately so when the abnormalities were found Conclusion is not suitable for the continuation of pregnancy on Tuesday need to administer drugs to terminate the pregnancy surgery will make the operation too difficult and increase the risk of the mother any sex Amniocentesis is a method of prenatal personal diagnosis generally countless suitable for prenatal diagnosis of mid-term pregnancy responsible for the diagnosis of amniotic fluid exists in the amniotic membrane cavity; the fertilized egg is formed on the seventh day of fertilization amniotic membrane cavity began to compare the production of amniotic fluid gestation weeks of the amniotic fluid volume of milliliters at the time of the week of ml weeks of ml weeks of ml weeks of ml weeks -The amount of amniotic fluid decreases slightly near the due date The best time for the prenatal diagnostic specialist to extract amniotic fluid by puncture is ~ weeks of gestation because I do not understand that this is only the fetus is small amniotic fluid is relatively large fetus is kindly floating in the amniotic fluid is surrounded by a wide band of amniotic fluid it is not easy to puncture with a needle to extract the amniotic fluid is not aware of the fetus extracted ml amniotic fluid only accounted for the total amount of amniotic fluid / ~ / smooth and will not cause the uterine cavity to suddenly become smaller and miscarriage and go home. And go home this period of time amniotic fluid in the largest proportion of viable cells cell culture viability can be used for film staining for fetal smile karyotype normal analysis of chromosomal genetic disease diagnosis of normal and gender determination can also be used amniotic fluid cellular DNA to make the same diagnosis of genetic disorders metabolic disorders indicated diagnosis determination of amniotic fluid alpha-fetoprotein can also be used to diagnose the baby's special needs of the fetus open neural tube deformities, etc. Amniocentesis in late pregnancy Too difficult to check can be measured blood type bilirubin lecithin sphingomyelin placental lactogen, etc. to understand the presence of maternal and child blood group incompatibility hemolysis immobility fetal lung maturity skin maturity placental function, etc. Steps of amniocentesis: amniocentesis steps are as follows with the indications of pregnant women to do ultrasound to determine the location of the placenta fetal special needs of the child to avoid injuring the placenta if there is no B ultrasound palpation to find the capsule sexy and large easy to touch the floating fetal body parts of the body can also be avoided placenta After selecting the point of entry, disinfect the skin and lay a disinfected towel for local anesthesia with a lumbar puncture needle with a needle core in the selected point of vertical stabbing; the needle through the abdominal wall and the uterine wall when there are two falling sensation to take out the core of the needle; with a ml syringe to aspirate amniotic fluid ml to be discarded in this section of the amniotic fluid to communicate with the possible inclusion of mother's cells; and then ml of amniotic fluid ml to be aspirated with a ml empty needle in a sterilized test tube with a cap; take out the head of the needle and cover the sterilized gauze to pressure -minutes have seen pregnant women bed rest carefully hours removed amniotic fluid centrifugation ~ recognize more than a minute clear liquid for biochemical tests sediment for cell culture or extraction of DNA for those who are suitable for amniocentesis: do amniocentesis is in order to screen for chromosomal aberrations in order to reduce the birth of stupid children stupid children because of the ticket vendors of this type of birth defects if the red packet can not be screened out for future home children and even shielded life children can not take care of themselves to bring a heavy burden on the family but Shunxin not all refused pregnant women have to undergo amniocentesis diagnosis in general the age of more than one year old high-risk maternal Tuesday recommended to do amniocentesis because of the mid-meal pregnant women over the age of the proportion of children born stupid children than pregnant women under the age of one year old to times However, amniocentesis is not a mandatory for this group of people in the medical style but in order to cuddle the health of the next generation does not deserve can doctors recommend to help the best to do amniocentesis and although the age of the age of less than one year, but after doing intravenous Down's syndrome screening found that there are high-risk factors for the sake of insurance should also what should be done by amniocentesis in addition to the pregnant women who have had a chromosomal abnormality of the child of an emergency powerful for the sake of a variety of the next generation's health must be done by amniocentesis; and the pregnant women who have been in contact with toxic substances radiation during pregnancy fetus injury Also half a year may be adversely affected by the Saturday so amniocentesis also have to do to avoid future regrets Amniocentesis terrible: in fact, amniocentesis is not as terrible as some pregnant women think amniocentesis method is the main ideal is to use a needle to extract a certain amount of amniotic fluid and its powerful process is in fact just like an intramuscular injection is that is why the pregnant woman does not need to be too nervous JenJu and the results of the current amniocentesis are bang in the ultrasound to do under surveillance rather than directly as before The amniocentesis is now done under the supervision of ultrasound rather than directly "blind" as in the past, so amniocentesis is not dangerous to the responsible fetus again Saturday only for some pregnant women with high risk factors for miscarriage may previously have a risk of miscarriage heartland such as uterine fibroids pregnant women in early pregnancy with frequent contractions and vaginal bleeding and other symptoms of preeclampsia pregnant women deal with the expert reminds It is necessary to do amniocentesis pregnant women should also be careful to send the choice of medical institutions it is understood that at present know Beijing maternity communication hospital clear Beijing Union can not condition hospital Beida discomfort hospital Beida people's hospital conditioning BeiMedSanYuan and several other medical institutions prenatal medical diagnostic center indifference by the Beijing often the city health bureau approval can easily carry out the amniocentesis project amniocentesis introduction Now, every pregnant woman in the 16 ~ 18 weeks of pregnancy will receive a perinatal diagnostic center, the hospital will be able to carry out the amniocentesis program, and the amniocentesis program can be easily carried out. Nowadays, every pregnant woman in her 16th to 18th week of pregnancy will receive an "Informed Consent for Prenatal Screening for Down's Syndrome" from the perinatologist. If the result of the Down's Screening is "High Risk", the doctor will usually recommend the pregnant woman to do further tests, such as doing the Down's Screening again or amniocentesis, in order to rule out fetal malformations. However, many pregnant women now refuse to undergo amniocentesis for fear of increasing the possibility of miscarriage. What is amniocentesis all about and is it really that scary?　　-What is amniocentesis?　　-What are the fetal diseases that can be detected by using amniotic fluid?　　-Is amniocentesis painful?　　-What is the chance of miscarriage after amniocentesis?　　-Will the development of the fetus be affected after amniocentesis?　　-Will amniocentesis harm the fetus?　　-What are the discomforts that may occur after amniocentesis?　　1. What is amniocentesis? Under ultrasound guidance, a long thin needle is inserted through the abdominal and uterine walls of the pregnant woman into the amniotic cavity to extract some amniotic fluid.　　2, the use of amniotic fluid can check those fetal diseases? The amniotic fluid is extracted to analyze the chromosome composition of the fetus, the most important and common is Down's syndrome. Some single-gene diseases, such as beta-marine anemia, hemophilia, etc., can be diagnosed by examining the genes (DNA composition) in the amniotic fluid cells. In addition, there are some major defects on the fetal surface, such as spina bifida, bulging meninges, bulging umbilical cord, split abdominal wall, etc., which can also be quantified by quantifying alpha-fetoprotein in the amniotic fluid, and get a fairly good reference value. Li Aoshang, Department of Obstetrics, Mianyang People's Hospital 3. What is the best time for amniocentesis? The best time for amniocentesis is around 16 weeks of pregnancy, i.e. 14 to 18 weeks. If the amniotic fluid is less than 14 weeks, amniocentesis is more difficult; if the weeks are too big, for example, more than 22 weeks, the fetus may be too big when the diagnosis is made, which will cause a lot of trouble and harm if the pregnancy has to be terminated.　　4. Will the amount of amniotic fluid decrease after amniocentesis and will it affect the development of the fetus? Most of the amniotic fluid comes from the urine of the fetus. In mid-pregnancy, the amniotic fluid volume is at least 250CC. During amniocentesis, about 20 cc of amniotic fluid is usually extracted, which accounts for less than 8% of the overall amniotic fluid volume and will be replenished soon, so there is no need to worry about the above problems.　　5、Will amniocentesis be painful and do I need to take an anesthetic injection? Although the needle used for amniocentesis is long (about 10 centimeters), the diameter of the tube is very small, which is even thinner than that of the needle used for blood sampling. Moreover, the nerves in the belly of a pregnant woman are more sparsely distributed, so she is not sensitive to the sensation of the needle sticking in her belly. Generally speaking, amniocentesis is at most the same as blood sampling and is not very painful, so local anesthesia is not necessary. Even if anesthesia is needed, the first injection will still hurt. Therefore, local anesthesia is unnecessary and may increase the risk of drug allergy or infection.　　6、What is the chance of fetal miscarriage after amniocentesis? No more than 3 out of 1000. The United Kingdom and the United States have conducted large-scale surveys and obtained such results. NTUH has also performed more than 15,000 cases of amniocentesis so far, and the results are similar to those reported in the United Kingdom and the United States.　　7. After amniocentesis, besides the extremely low miscarriage rate, will the fetus be injured? Amniocentesis performed under continuous ultrasound guidance will not harm the baby, although pregnant women may still be concerned. The main reason for this is that some pregnant women have had friends and relatives who have given birth to defective children after undergoing amniocentesis. Many people have the wrong idea that once amniocentesis is performed, all fetal abnormalities are caused by it. In fact, this idea is completely illogical. Even if the chromosomes are normal, about 2% of newborns have some kind of defect. These problems have nothing to do with chromosomes and there is no way to diagnose them using amniotic fluid analysis. These defects would still be present even if the mother had not undergone amniocentesis in the first place. It is not reasonable for people to blame a specific test for all newborn malformations.　　8. What are the discomforts that may occur after amniocentesis? There may be some pain at the place where the needle is inserted, which is the same as an injection or blood draw. Very few pregnant women have a little bit of vaginal bleeding or a little bit of discharge, which usually disappears naturally after a little rest or within a few days. However, if there is severe abdominal pain or fever, or if the water breaks, you should seek medical attention. The chances of these serious complications are less than three in a thousand.　　9. Is there anything I need to pay special attention to after amniocentesis? Generally speaking, except for heavy work, you can continue with your normal work as usual. You do not need to take injections or medication, and you can just follow your normal routine.　　10、How long will it take to get the chromosome analysis result after amniocentesis? About two to three weeks. The chromosome analysis of amniotic fluid cells is not like the general examination, where the results can be obtained very soon after the amniotic fluid is put into the machine. The extracted cells have to be cultured to divide to a sufficient number, a process that usually takes about five to ten days. After that, the chromosomes have to be stained, observed, photographed, enlarged, cut and pasted, and scrutinized, so it takes such a long time.　　11. There are some reports that fetal chromosomal abnormalities can be detected from the mother's blood without going through amniocentesis, is this true? It is the ultimate goal of scientists to detect chromosomal abnormalities in the fetus directly from the mother's blood. So far, however, with the exception of a very few special cases, this goal has remained largely unattainable. Although the scientific community has long confirmed that fetal cells are present in maternal blood, the number of these cells is extremely rare. Examining these cells may be more difficult than finding a needle in a haystack. It should also be noted that maternal blood screening for Down's syndrome is very different from amniocentesis. Maternal blood screening can only calculate the chance of the fetus developing Down's syndrome, whereas amniocentesis can diagnose Down's syndrome.　　12. If the result of amniocentesis is normal, does it mean that everything is fine with the fetus? Generally speaking, amniocentesis is only a chromosomal test. If the result is normal, it only means that there is no problem with the chromosomes (the most common and important one is Down's Syndrome), but it cannot rule out other non-chromosomal diseases, such as most congenital heart diseases, mental retardation, cleft lip and palate, as well as problems caused by genes. In other words, even if the chromosomal test results are normal, about 2% of babies are still born with certain abnormalities.　　13. What is the success and accuracy rate of chromosome testing with amniotic fluid cells? The success rate of the test is over 99%. In a few cases, the amniotic fluid cells are not able to grow due to severe contamination of the mother's blood. Other factors may prevent the cells from growing. At this point, the amniotic fluid may have to be redrawn. Chromosome results are correct more than 99.8% of the time. In a few cases, due to contamination of the mother's blood cells, chromosomal abnormalities are characterized by a very small percentage of errors.　　14. Why is it that in some cases, after amniocentesis, the physician recommends that the couple return for blood sampling for comparison? In a few cases, the amniotic fluid cells may have structural abnormalities. For example, the A and B chromosomes are each broken at one point; the chromosome that is broken from A is attached to the B chromosome, and similarly, the chromosome that is broken from B is attached to the A chromosome. During the process of chromosome breakage and reorganization, some important genes may be damaged, resulting in certain defects, the most common of which is mental retardation. However, some chromosome breakage and reorganization does not harm the genes, so there is no harm to the baby. If a similar phenomenon is found during the amniotic fluid test, the physician must first find out the chromosome composition of the parents. If the father or mother has the same abnormality as the fetus, and the parents themselves do not have any abnormality, it means that this chromosome variation will not cause problems in the family, and the pregnancy can continue intermittently. On the other hand, if the chromosomes of both husband and wife are normal, but only the chromosomes of the fetus are abnormal in structure, then the fetus may have a 5% to 10% chance of having some defects, especially mental problems. When a physician encounters such a chromosomal rearrangement, he or she will first examine the chromosomal composition of the parents in order to assess the possible effects on the fetus.　　What is chorionic villus sampling? Placental tissues appear as villi when magnified, so the villi are the smallest units that make up the placenta. Under ultrasound guidance, a catheter or needle is inserted into the placental tissue through the cervix or abdomen and a small amount of chorionic villi is aspirated for chromosomal, genetic, or enzyme analysis to diagnose chromosomal or genetic abnormalities of the fetus, which is called chorionic villus sampling.　　16. When is the appropriate time for chorionic villus sampling? According to many studies around the world, chorionic villus sampling can be done after 10 weeks of pregnancy (counting from the start date of the last menstrual period). The World Health Organization has tracked more than 210,000 pregnant women who underwent chorionic villus sampling and found that chorionic villus sampling after the 10th week of pregnancy does not increase the chances of miscarriage (about 1%) and does not lead to malformations in the newborn, such as limb defects.　　17. What are the two types of chorionic villus sampling? What are the main differences? There are two types of chorionic villus sampling: transcervical and transabdominal, depending on the route of sampling. When sampling through the cervix, the bladder of the pregnant woman usually needs to have some urine, just like internal examination, the pregnant woman has to take off her pants and lie down on the examination table, and the physician has to open the vagina with a vaginal dilator before sampling. The time to use this route is between 10 and 13 weeks of pregnancy. For transabdominal sampling, the pregnant woman simply lies flat on a regular examining table, and a long, thin needle is inserted through the belly and uterine wall to enter the placenta to collect chorionic villi. It can be used from the 10th week of pregnancy to full term. Transabdominal chorionic villus sampling can be used in the majority of cases, but in rare cases, because the entire placenta is located in the posterior wall of the uterus, chorionic villi are technically less easily collected.　　18. What are the diseases that can be detected by chorionic villus sampling? Fetal chromosomal abnormalities and single gene disorders. Basically, chorionic villus sampling can detect similar diseases as amniocentesis. However, the diagnosis of certain genetic diseases requires a larger amount of DNA, such as alpha-marine anemia, etc. In this case, chorionic villus is better than amniocentesis.　　19. Is anesthesia required for chorionic villus sampling? No anesthesia is required for either cervical or abdominal sampling. For cervical sampling, there will be a sensation of urine because the bladder needs to be inflated, but there is no pain during sampling. For abdominal sampling, although the needle used is slightly thicker than that used for amniocentesis, it is not very painful, so there is no need to worry.　　20. Is it possible to use chorionic villus sampling or amniocentesis to check the health of the fetus by taking medication or taking X-rays in early pregnancy? Basically, only 1 to 2% of all fetal malformations are caused by medication or X-rays. Even if there is an effect, it usually does not change the chromosomal or genetic composition, so chorionic villus sampling or amniocentesis is not helpful in these cases.　　21. Do pregnant women who undergo chorionic villus sampling need to pay special attention afterwards? Generally speaking, no special attention is needed; daily activities can be carried out as usual. For transcervical sampling, there will almost always be a small amount of vaginal bleeding in the first few days after the procedure. For those who undergo transabdominal sampling, there is more or less pain at the site of the needle puncture, and a few people may have some vaginal bleeding, which is normal and not a cause for concern. If there are some special symptoms, such as heavy bleeding, premature rupture of membranes, severe pain in the lower abdomen, or fever, you should consult a doctor as soon as possible.　　22. How long does it take to get the report after the villus sampling? It depends on the items to be examined. If the test is to check chromosomes, like amniotic fluid cells, the chorionic villus cells have to be cultured and analyzed, and it usually takes about two weeks to get the chromosome diagnosis. If the test is for a single gene disease, it may take as short as one week or as long as three weeks to get a report.　　23. What are the chances that a person undergoing amniocentesis or chorionic villus sampling will have an abnormal test report? Generally speaking, the rate of chromosomal abnormalities is around 2-4%, while the rate of recessive genetic diseases is 25% and the rate of dominant genetic diseases is 50%.　　24. How many genes are there in human beings? How many genetic diseases can be diagnosed at present? Human beings have about 100,000 genes distributed over 23 pairs of chromosomes. Unfortunately, the number of genes that are well understood by the scientific community worldwide is not very large, only a few hundred, so many genetic diseases cannot be diagnosed prenatally at present. Europe, the United States and Japan are actively engaged in the human genome research program, and it is hoped that in the next few years the entire sequence of human DNA will be understood. Once this program is completed, it will make a significant contribution to the study and diagnosis of single genes.　　25. How many single-gene diseases can be diagnosed by amniocentesis or chorionic villus sampling in China at present? Some single-gene disorders are very rare, while others do not have serious symptoms and do not require prenatal diagnosis. Currently, there are more than 10 single-gene disorders that are more commonly diagnosed prenatally in China, such as marine anaemia A and B, haemophilia A and B, Duchenne muscular dystrophy, fragile X chromosome disorder, glycogen storage disorders I and II, congenital adrenal hyperplasia, male feminization disorder, Huntington's dance disorder, phenylketonuria, spinal muscular dystrophy, neurofibromatosis type I, adult polycystic kidney disease, and a few mucopolysaccharidoses, among others. , a few mucopolysaccharidoses, etc. Although amniotic fluid diagnosis is almost 100% accurate in detecting chromosomes, it cannot detect structural disorders like clubfoot or heart disease.