Preimplantation Genetic Screening (PGS) is an early prenatal screening method to detect chromosomal number and structural abnormalities in early embryos before implantation and implantation, and to analyze whether the embryo has abnormal genetic material by detecting the structure and number of 23 pairs of chromosomes in the embryo at one time. Thereby, normal embryos are selected for implantation into the uterus with the aim of obtaining a normal pregnancy, improving the clinical pregnancy rate of patients and reducing multiple pregnancies. Significance of pre-implantation genetic screening The emergence of PGS is the result of rapid development of assisted reproduction and molecular biology techniques. The application of PGS technology is significant by selecting normal embryos. 1. PGS can select healthy embryos, improve IVF success rate and reduce miscarriage rate Compared with traditional embryo morphology which relies on microscopic techniques and selects embryos with high morphological grade for transfer, PGS can directly analyze the genetic material of embryos to accurately determine whether there are chromosomal abnormalities in embryos and screen out truly healthy embryos. Data from clinical trials have shown that PGS can reduce the miscarriage rate from 33.5% to 6.9% in people undergoing assisted reproduction treatment for recurrent miscarriages, while increasing the clinical pregnancy rate from 45.8% to 70.9% in morphology-dependent cases. The newly published results show that PGS can significantly improve all indicators of IVF, and that PGS can significantly improve all indicators of first- and second-generation IVF, fundamentally increasing the pregnancy success rate of first- and second-generation IVF. Reduce the rate of spontaneous abortion and improve the quality of pregnancy. The average success rate of IVF is 20-30%. In order to increase the success rate of one implantation, 2-3 embryos are usually implanted at the same time, so there are often some multiple pregnancies. Multiple births are more risky than single births, and this risk exists for both the mother and the child. Authoritative surveys have found a 78.45% cesarean delivery rate for twins, 47.07% preterm births, and 39.7% comorbidities and complications. Mothers of twins as well as multiple births are more likely to develop pregnancy syndromes such as diabetes and hypertension during pregnancy, and have a higher probability of postpartum hemorrhage, as well as being more likely to have preterm births. Most of the children born prematurely will develop congenital lung disease, and this disease will be lifelong. Therefore, in order to protect the safety of mother and child, triplets or more, in principle, require an abortive procedure, which has a 10% chance of causing abortion of all embryos. Reproductive medicine specialists have always recommended that if IVF is used, it is best to receive only one fertilized egg for transfer, and he does not recommend IVF for twins, as this method does not provide much benefit to the mother and child. Although not mandatory, if embryos are transferred to a woman and she ends up with twins, this transfer by the doctor is usually considered an unsuccessful transfer. By using PGS technology to select healthy embryos and increase the success rate of IVF, the harm and ethical conflicts caused by multiple embryos being blindly transferred to increase the success rate of pregnancy, resulting in multiple pregnancies and having to perform reduction during pregnancy can be avoided. PGS is suitable for pregnant women of advanced age (age ≥ 35 years); pregnant women with a history of recurrent spontaneous abortions (≥ 3 spontaneous abortions); pregnant women with recurrent embryo implantation failures (≥ 3 failures); couples who have given birth to children with chromosomal abnormalities; couples with abnormal chromosome number and structure; couples who have a strong desire to Pre-implantation genetic screening considerations With the choice of PGS, routine prenatal screening should still not be neglected. This is because there are more than 4,000 various genetic disorders worldwide, and PGS can currently only check for abnormalities in the structure and number of the 23 pairs of chromosomes in the embryo and cannot cover all of them. Although this does not affect the normal development of the embryo, the genetic composition of the cells taken and those left behind for further development are not identical, so the screening results may not match for some chromosomal chimeric diseases. In addition, the cause of chromosomal disorders is still unknown and there is no way to prevent them. Although healthy embryos are selected, chromosomal abnormalities may occur at any stage of fetal development after embryo transfer due to maternal causes, environmental factors and other factors. Therefore, after choosing PGS for successful conception, pregnant women still need to undergo routine prenatal screening. PGS is not a substitute for prenatal screening. If fetal abnormalities are found during routine prenatal checkups, or if the pregnant woman herself has indications for prenatal screening, she is strongly advised to choose prenatal screening methods such as amniocentesis for confirmation.