As mothers-to-be know, a test called Down’s syndrome screening is done during pregnancy, and further amniocentesis is required if the report suggests abnormalities. So what is the Down’s syndrome screening test? Can it detect all congenital disorders of the fetus? First of all, let’s introduce Down syndrome. Down syndrome is a congenital disorder, also known as congenital dysmorphism or Down syndrome, caused by chromosomal abnormalities (an extra chromosome 21). 60% of affected children are aborted in early fetal life, and those who survive have significant intellectual backwardness, peculiar facial features, growth disorders and multiple malformations. Since the disease is related to genetic material, there is no fundamental treatment after birth, and therefore it can place a heavy burden on families and society. Modern medicine confirms that there is a correlation between the incidence of Down syndrome and the mother’s age of pregnancy, which is an abnormality of chromosome 21, and that advanced maternal age and aging eggs are important reasons for the occurrence of non-separation. Our human genetic material is 23 pairs of chromosomes, 23 from the mother and 23 from the father. When the sperm and egg are formed, they go through cell division and are meiotic, so that the sperm and egg each have 23 chromosomes inside, and the egg is fertilized and then paired into 23 pairs of chromosomes to become a new life. However, if the mother is too old, her egg cells are aging, and it is possible that a pair of chromosomes did not separate during the egg formation process, then the offspring will be abnormal because they are not 23 pairs of chromosomes after the fertilization of an egg with one extra chromosome or one missing chromosome. Down’s syndrome is an extra chromosome 21. At present, we are screening for three main diseases: 1. Down syndrome, trisomy 21, which is the most common congenital disease caused by chromosomal abnormalities; 2. Edwards syndrome, trisomy 18, which is the second most common chromosomal disease after Down syndrome. Down’s syndrome screening, which is the measurement of the amount of serum markers through blood sampling, combined with the pregnant woman’s age, weight, week of pregnancy and ultrasound indicators, through software to calculate the risk of the pregnant woman’s current fetus suffering from trisomy 21, trisomy 18 and neural tube defects. Neural tube defects are deformities such as anencephaly and spina bifida, which are severe and non-viable, and mild and affect health. Because Down’s syndrome screening is a risk level calculated and analyzed through a combination of indicators, it is not the final means of confirming the diagnosis. We use this screening program to guide you on whether you should go for further confirmatory tests. As a screening program, there is a certain rate of false positives, that is, the Down’s syndrome screening tells you that you are at high risk, but the result of the amniocentesis is normal, so you may have a false alarm and suffer from the pain of the amniocentesis; or it may be a false negative, that is, the screening is low risk, but you may end up giving birth to a child with Down’s syndrome. In both cases, we as doctors feel sorry and helpless. Medical science is constantly evolving, and there are already tests for fetal chromosome analysis by taking blood from pregnant women, but they are not yet widely used in clinical practice. I believe that in the future there will be some non-invasive and accurate methods to help us make a diagnosis. For pregnant women who are at high risk for Down syndrome screening trisomy 21 and trisomy 18, and for those who are over 35 years old, we recommend that you get an amniocentesis. This is the test that can give you a definitive diagnosis. Amniocentesis is the extraction of amniotic fluid, which will contain cells shed from the skin of the fetus. These cells are collected to check the chromosomes of the fetus and to see directly whether the chromosome number and structure are normal. If it is normal, then continue the pregnancy, if not, then bear the pain. There is a time requirement for amniocentesis, usually at 16-20 weeks, when there is more amniotic fluid and it is not advisable to injure the fetus, and the cells in the amniotic fluid are highly viable and easy to culture. Of course, there are individual hospitals that have expanded the time frame for amniocentesis. If you are in a high-risk group, you can also have a chorionic villus biopsy for screening in early pregnancy. So is a chromosome test needed for those who suggest a high risk of neural tube abnormality? Neural tube abnormality is not a chromosomal disorder, that is, it is not an abnormality in the number or structure of chromosomes, it is a genetic disorder. The diagnosis cannot be confirmed by chromosomal examination, so amniocentesis is not required. However, neural tube abnormality, which affects the head and spine, can be diagnosed with ultrasound. Therefore, during 18-23 weeks of gestation, when the fetal organs are fully developed, the ultrasonographer can detect this malformation by careful observation. As I said earlier, other chromosomes may also occur during egg formation, so can other chromosomal trisomies be formed? It is entirely possible, but most embryos with other chromosomal trisomies are aborted early in life and very few survive, so there is no targeted screening. Does the advanced age of the mother, which is a risk factor for chromosomal abnormalities, have an effect on the advanced age of the father? This starts with the occurrence of eggs and sperm. Eggs are formed when the girl is still an embryo and are present in the ovary in the form of oocytes, which are limited in number, about 4 million at birth, in a dormant state, and still retain 400,000 by puberty. At the beginning of puberty, hundreds or thousands of oocytes awaken each month and continue meiosis to form eggs. However, eventually only 1-2 eggs are formed each month, and the rest of the oocytes die at various stages of development. Thus, from puberty to menopause, a total of about 400 eggs are ovulated. The first egg is expelled after a wait of about 15 years, and the last egg is expelled after a wait of half a century. During the long wait the eggs also slowly age and may be subject to adverse stimuli such as drugs and radiation. The number of sperm produced per gram of testicular tissue after puberty ranges from 3 to 7 million in 24 hours, and the entire cycle takes only 16 days. If the sperm is not expelled, it will be absorbed by the body. The sperm that are fertilized are relatively fresh. The eggs excluded by older mothers may be of “antique” quality. These diseases cannot be cured, and even if they can be diagnosed through pregnancy screening, amniotic fluid extraction, and ultrasound, they are still diagnosed after the middle of pregnancy, and once a miscarriage is detected, it can cause certain psychological and physical damage to the mother. 1, before pregnancy and early pregnancy to take folic acid, can reduce the occurrence of neural tube malformation. So it is highly recommended to start taking folic acid before pregnancy, especially for areas and people who eat less vegetables and fruits. 2.Marriage and childbirth at a suitable age can reduce the occurrence of 21 three days and 18 trisomy. 3, regular maternity checkups during pregnancy can detect these abnormalities in time. Finally, I tell you that the so-called Down’s syndrome screening program is only for trisomy 21, trisomy 18 and neural tube abnormalities. It cannot check for all chromosomal abnormalities, let alone all congenital diseases.