Pre-implantation genetic screening (PGS) technology has long lifted its veil of secrecy and entered the vision of the general public. Many infertile couples preparing for IVF also ask whether they can do “third generation IVF” to select embryos and customize a perfect baby. Subconsciously, people think that when buying a cell phone, they should choose a new generation product, so shouldn’t they also choose the “highest level”? Should every embryo be PGS? The proportion of IVF babies born in Western countries is 1% to 3% of the total number of newborns every year since the beginning of this century, and the proportion of IVF babies born in China has exceeded 1% in 2012, and this proportion is increasing year by year. People are gradually becoming more and more satisfied with the IVF technology to get a child, and want to have a custom-made perfect baby. And what is the “highest level” of IVF? In fact, the third generation of IVF technology that people refer to as embryo selection is also known as Preimplantation Genetic Diagnosis (PGD)/ Screening (PGS). What is PGS? Pre-implantation Genetic Screening (PGS) is the process of screening embryos for chromosomes to eliminate aneuploid embryos and select normal embryos for implantation during the IVF procedure with the aim of improving IVF outcomes. In short, the new testing technology is used to select the right potential stock – the embryo seeds for implantation. Which patients are suitable for PGS? There is an international consensus that PGS technology is suitable for these categories: 1. female partner is older than 35 years old (AMA); 2. recurrent spontaneous abortions at 2 or more times (RM); 3. recurrent implantation failure (RIF), high scoring embryos transferred 3 or more times without pregnancy; 4. severe male infertility (SMF), severe oligospermia and teratospermia in male partner. 5, Other: selective single embryo transfer (eSET), etc. Multiple pregnancies, including twin pregnancies, are recognized as complications of assisted conception, and miscarriage, preterm delivery and other obstetrical complications associated with multiple pregnancies are a constant concern in the industry, and it is the consensus of many experts in the field to reduce the number of embryos transferred and the rate of multiple pregnancies. The ability of PGS to perform chromosome group screening to select the right seeds of potential embryos has become an important method. The debate: Does every IVF need PGS and does PGS improve the clinical pregnancy rate in IVF? Expert opinion on this issue is not unanimous, and the 2010 American Society for Reproductive Medicine (ASRM) had a heated professional debate on this issue. 1. The debate came down to: the risks of embryo biopsy retrieval and the limitations of diagnostic techniques. The pro side of the debate argued that PGS can improve embryo implantation and clinical pregnancy rates and reduce miscarriage rates by testing for appropriate embryos for transfer; the con side of the debate retrospectively analyzed previous PGS literature data and concluded that PGS did not significantly improve embryo implantation and clinical pregnancy rates. The opposing side argued the potential risk of damage to the embryo from biopsy sampling and the limitations of the testing technique itself. The previously used multicolor fluorescence in situ hybridization technique can only detect a limited number of chromosomes and the results are not comprehensive. Thus, it is believed that PGS does not really benefit patients. The counter argument of the positive side: some of the PGS reported in the literature did not significantly improve the clinical outcome, which may be related to the uneven biopsy techniques of individual centers, where the success rate of PGS is significantly higher in centers with mature biopsy techniques. It is also true that there are limitations in testing technology, and the inconsistent range of chromosomes tested at different institutions is an important reason, as the greater the range of testing, the higher the success rate. What exactly is the conclusion? After several years of development of molecular diagnostic technology, there has been a breakthrough in detection technology. Microarray technology and sequencing technology can obtain the information of the whole chromosome group at the same time, which greatly improves the accuracy of the diagnosis, so that the limitation of the detection technology is solved. 2. Another focal point of the debate is the potential risk of embryo damage from the sampling biopsy itself. In recent years, blastocyst biopsy has gradually replaced the previous day 3 embryo biopsy, so the potential risk of damage to the embryo by the biopsy technique has been largely resolved. At this point, the debate about PGS has come to an end, and the summary data from the 2014 European Society for Reproduction (ESHRE) Annual Meeting on PGS show that embryo screening using blastocyst biopsy combined with new whole genome microarray or sequencing technologies has become the standard for PGS, which can improve embryo placement rates and reduce miscarriage rates, and can be an effective measure for selective single embryo transfer to improve assisted conception outcomes. The conclusion seems to be clear that PGS can improve embryo fertilization rate and reduce miscarriage rate, does it mean that PGS should be promoted clinically? The answer is not quite true, as the relative complexity and cost of PGS and the reduction in the number of embryos available for transfer are still controversial compared to the benefits it brings. It is believed that this question of health economics will be answered with the expansion of the sample size. (Figure: Oogenesis (D3) embryo biopsy retrieval and blastocyst (D5) embryo biopsy retrieval) Conclusion: PGS has clear clinical indications, and the need for PGS needs to be evaluated based on the circumstances of the patient couple and the medical institution.