1. Age Age is the most important factor in determining the success rate. The gradual decline of ovarian function in women with age is an inevitable trend and a process that is difficult to reverse. In women, ovarian reserve function starts to decline after the age of 35, and is significantly reduced by the age of 40-42, resulting in a significant decrease in fertility. Declining ovarian reserve predicts a low number of eggs and poor egg quality during IVF, resulting in poor embryo quality or even the possibility of no embryo transfer. Those older than 45 years old or with very poor ovarian reserve have a very low IVF success rate (less than 5%) and are advised to give up trying. If you are younger than 35 years old, with normal ovarian reserve and good uterine conditions, the success rate of IVF can reach 40-50%, and there is a cumulative chance of success if you have frozen embryos. 2. Ovarian reserve function The function of the ovaries can be assessed by blood hormones on day 2-4 of the natural cycle and the number of sinus follicles measured by ultrasound. There are individual differences in ovarian function, therefore, the doctor needs to assess the ovarian function of the patient before setting the protocol and then develop the protocol accordingly. Patients with a high number of sinus follicles and normal basal FSH levels have good ovarian function and a high success rate of IVF. 3. Uterine factors Patients with combined uterine pathology have low IVF success rate, such as uterine adhesions, submucosal fibroids, longitudinal uterus, history of endometrial tuberculosis, endometritis and repeated scraping to thin endometrium. Hydrosalpinx affects embryo implantation because the retained fluid can flow into the uterine cavity. Hysteroscopy allows for accurate evaluation and treatment of uterine cavity lesions. Vaginal ultrasound to see the endometrial blood flow is an assessment of the normal uterine cavity lining and can predict the success rate of quality embryos after transfer. 4. Frequency of IVF As the number of failed IVF treatments increases, the chance of obtaining success with another treatment decreases. Studies have shown that patients who have attempted IVF four times to retrieve eggs have very little chance of obtaining a successful pregnancy and in principle should give up trying to continue IVF for pregnancy. 5. Lifestyle and mental status Unhealthy lifestyle is not good for IVF success, such as smoking, drinking and staying up late. Excessive stress, anxiety and depression are also a cause of failure. Therefore, before and after IVF, you should maintain a healthy lifestyle and try to be relaxed, happy and confident.