Multiple factors decide if a pregnancy via IVF can be successful or not. Some of them are under your control while others are not. You can work and discuss with your doctor to determine how you can increase your chances of getting pregnant through IVF. Here are some of those factors:
Your cause of infertility
Health conditions
The success rate of the fertility clinic
Number of IVF cycles
Using donor eggs or your own
Total number of pregnancies
Number of previous births you have had
Your weight and height
Your age