The success rate of pregnancy with IVF and IUI is not 100%. What causes its failure? Here are 5 important factors that affect the success rate of IVF. IVF, or artificial insemination, has become one of the standard operations for infertility treatment. However, the success rate of IVF and IUI pregnancy is still not 100%, there are still some factors that can affect the success rate of IVF and IUI. Some people are able to get pregnant after one IUI; some people are able to get pregnant after one IVF; but some people have done IVF many times and still can’t succeed. Even need to do 5 to 6 times before success, what are the factors that affect these successes and failures? If the number of spermatozoa per cc is less than 10 million or the motility is less than 30%, IVF is recommended and not suitable for IUI; if the number of spermatozoa per cc is less than 5 million or the motility is less than 20%, IVF is recommended instead of gift baby; if the number of spermatozoa per cc is less than 1 million or the motility is less than 10%, ICF is required. If less than one million per cc or less than 10% motility, ICSI (single sperm microinjection) IVF is required. 2. Egg quality: The older a woman is, the worse the egg quality is. Over 35 years old, the quality of the eggs starts to age, over 38 years old the success rate is less than 50%, the success rate will be discounted and will be right, and over 40 years old, the success rate is only 30% of the young. 3, the quality of embryos: the quality of embryos, is an important factor in the success rate of IVF, good embryos are easy to succeed, bad embryos are not easy to succeed. So, three good embryos have a 25% to 30% pregnancy rate. Of course implanting more embryos is more likely to be successful, but it relatively also increases the risk of multiple births. Good embryos come from good eggs, good sperm and a stable laboratory culture system. 4. Embryo implantation procedure: It is one of the essential elements of successful IVF. Properly placing embryos in a position where they can easily be implanted can easily increase the success rate. “The success rate of “gift baby” is about 40-50% when the egg and semen are placed in the fallopian tube, and about 40-50% when TET is performed. Because there are some factors in the fallopian tube that are beneficial to embryo culture. If sperm, eggs or embryos are placed in the fallopian tube, it will increase the success rate of IVF. 5. Quality of the endometrium: The endometrium is the place where the embryo is implanted. If the endometrium is thick enough, rich in blood flow and with good cell division, it will increase the embryo implantation rate. On the contrary, if the endometrium is too thin, with insufficient blood flow and lack of hormonal secretion, the embryo will not be easily implanted. When the embryo is implanted, the uterus will contract and sometimes the embryo may even be pushed into the fallopian tube and become ectopic, a rate as high as 5-7%. Therefore, it is important to take sufficient bed rest and luteinizing hormone after embryo implantation to increase the rate of implantation and reduce the rate of ectopic pregnancy.