The main factors that determine the success of IVF are: the quality of the embryo, the receptivity of the endometrium and the match between the two. It is like the relationship between seed and soil: the embryo is the seed, the endometrium is the soil, and the match between the two is the right time to plant the seed. In addition, personal physical health and psychological factors also play a big role in improving the success rate of IVF. Embryo quality Currently, the quality of embryos is mainly assessed by observing the morphology and developmental speed of embryos, which is simple, easy and non-destructive. However, it is difficult to predict the developmental potential of embryos with an accuracy of about 60-70%. It is generally accepted that 36-48 hours after insemination, development to the 6-8 cell stage is the normal developmental rate of the embryo. Before transferring embryos, the quality of the embryos is taken into account and those with high developmental potential are selected for transfer, but the number of transferred embryos must be limited to avoid the occurrence of multiple births. Improving the quality of embryos starts with improving the quality of sperm and eggs, so conditioning both partners is fundamental, having a good diet and lifestyle habits, and necessary nutritional supplements will enhance fertility. Endometrial receptivity The endometrial receptivity is the acceptability of the endometrium to the embryo. The successful establishment of endometrial receptivity during embryo implantation is an essential factor to ensure successful embryo implantation, and there is no good indicator to assess endometrial receptivity. Currently, the commonly used clinical index for endometrial evaluation is the morphological assessment of the endometrium under vaginal ultrasound. The endometrium under ultrasound is divided into three types: type A: clear endometrial trilinear signs; type B: blurred visible trilinear signs; type C: disappearance of trilinear signs. Pre-transfer hysteroscopy can also exclude abnormal endometrial lesions. If patients with high embryo quality are not able to have a successful pregnancy after transplantation, hysteroscopy is recommended for this group of patients to exclude uterine cavity pathology. Suitable timing Whether transferring day 3 embryos or day 5 blastocysts, it is necessary to match the time of embryo cultivation in vitro with the time of endometrial transformation, and to transfer during the implantation window of endometrium in order to improve the success rate. 4. Physical condition and psychological state Heavy psychological stress can affect the endocrine level and therefore the success rate of IVF. High psychological stress often makes women nervous and causes disorder in uterine muscle contraction, resulting in embryo failure due to embryo failure. However, the number one cause of IVF failure is still age! As the ovaries gradually go into decline with age, the quality of eggs will get worse and the success rate of IVF will drop significantly due to the aging of egg cells and the chance of chromosomal aberrations increases significantly. At the same time, as age increases and physical quality decreases, pregnancy will place a great burden on the heart, kidneys and liver, and complications during pregnancy and delivery will increase in advanced maternal age, and the live birth rate will decrease. Therefore, parents who are planning to have a baby should hurry up.