1. Both of our couples are normal and have no family history of having a Down’s syndrome child even if they are at high risk for Down’s syndrome screening. Down’s syndrome is a chromosomal disorder that is randomly distributed in the normal population. Only about 3-5% of Down’s children are genetically related, i.e. one of the couple is a balanced chromosome translocation carrier, which can lead to the birth of a fetus with trisomy 21. The remaining 95-97% of fetuses with trisomy 21 have normal chromosomes in both parents. 2. Amniocentesis is a method to detect whether the fetus is smart or not. It is not. Down’s syndrome is one more chromosome 21 than normal. Therefore, pregnant women who undergo amniocentesis because they are at high risk for Down’s syndrome screening only check whether the fetus has normal chromosomes. Most fetuses with abnormal chromosomes are mentally retarded, but not all mental retardation is caused by chromosomal abnormalities. So normal amniotic fluid chromosomes can only indicate that the fetus is not trisomy 21. 3, amniocentesis fetal chromosomes are normal, the fetus must be normal. Not necessarily. Some fetuses may have one kind of malformation or another due to other reasons or unknown reasons, such as congenital heart disease, digestive tract malformation, etc. can only be diagnosed by ultrasound. So a chromosomally normal fetus must also undergo systematic ultrasound examination. 4. High risk of Down syndrome screening, the fetus must be trisomy 21. It is not. According to the clinical summary data, 3%-4% of pregnant women aged 35 and above with high risk of Down syndrome screening give birth to a fetus with trisomy 21, and 2%-3% of pregnant women aged below 35 with high risk of Down syndrome screening give birth to a fetus with trisomy 21. Therefore, the majority of pregnant women with high risk of Down syndrome screening have chromosomally normal fetuses. The appropriate gestational week for amniocentesis is generally 16-20 weeks in textbooks, but from years of clinical experience, the success rate of amniocentesis cell culture is highest at 20-24 weeks of pregnancy (based on ultrasound). If more than 24 weeks of gestation, umbilical vein puncture can be performed to detect the number and structural abnormalities of fetal chromosomes. It is also feasible to take amniotic fluid by amniocentesis and detect the number of abnormalities of chromosomes 13, 18, 21, X and Y by fluorescence in situ hybridization. 6.Do I need local anesthesia for amniocentesis? Amniocentesis is performed only through the skin and muscle layer into the amniotic cavity without local anesthesia. The use of anesthesia in mid-pregnancy is a potential risk to the fetus. 7. Is amniocentesis painful? Painful or not is related to each individual’s sensitivity to pain. Generally speaking, amniocentesis can be somewhat painful, but it is similar to the feeling of blood sampling from a vein. 8.What are the complications of amniocentesis? The most common complications of amniocentesis in Tianjin Medical University General Hospital are 3‰ of spontaneous abortion, 1‰ of intrauterine fetal death and 3‰ of cell culture failure. Other risks still exist, but are less likely to occur, such as amniotic fluid embolism and cerebrovascular accidents. 9. Can amniocentesis cause fetal malformation? Amniocentesis is performed at 20-24 weeks of gestation, when the fetal organs and limbs have been developed, and amniocentesis itself will not cause fetal malformation. 10. Can amniocentesis accidentally puncture the fetus? Although puncture is performed after ultrasound positioning, it is possible to accidentally puncture the fetus because the fetus is moving, but the probability of occurrence is small. The fetal activity is still mainly limb-based, so it is slightly more likely that the fetal limb will be punctured by mistake. 11.What is the accuracy rate of amniocentesis in diagnosing fetal chromosomal abnormalities? The Ministry of Health requires an accuracy rate of >98% for karyotype analysis. 12.How long does it take to get the diagnosis report after amniocentesis? The notification of prenatal diagnosis result can be obtained 3 weeks after amniocentesis.