There is no standard number of embryos that are implanted for all patients. Many factors influence how many embryos to transfer, including your age and medical history. However, to offer the highest chance of a safe and successful pregnancy, we always look to minimize the risk of multiple births (twins, etc.), which often means implanting as few eggs as possible.
It’s important to discuss your goals with your MD. If you want a single pregnancy, the approach to your cycle may be different than if you’re planning on a large family requiring several embryo transfers. The latter may indicate a cycle that creates a more significant number of embryos available for freezing and use in future cycles. The former may require lighter stimulation, reducing the number after the cycle is complete.