Age of women is the most important predictor of success as it determines quality of eggs. Apart from age,
women with a previous clinical pregnancy have lower pregnancy chances after IVF, but women who previously had given birth have higher pregnancy chances after IVF. Women with male subfertility or tuboperitoneal disease have lower pregnancy chances compared with those with unexplained infertility. Women with endometriosis always have lower success than with other factors. A positive association between increasing number of oocytes retrieved and pregnancy chances after IVF has been found. Women who yield 11 or more oocytes have higher success in IVF. Similarly, women where more than two embryos are transferred have significantly higher pregnancy chances. Lower morphology scores of embryos are also associated with lower pregnancy chances. Double-embryo transfer doubles the chance of pregnancy but also increases the risk of multiple pregnancy.