A dozen eggs might be just the right amount to buy at the grocery store. But when harvesting human eggs for in IVF, 15 is the magic number. Resulting in the greatest chances of a live birth. The results, based on a computer model using data from women receiving IVF treatment. Strike a balance between harvesting too few eggs and reducing the chances of a live birth with harvesting too many eggs and risking the potential of a negative health outcome for the mother. However, the number of harvested eggs should depend on the woman who is undergoing the IVF procedure. Her age, her hormone levels and other factors. The people in the study who had 20 or more eggs harvested were probably overstimulated. Which increases body levels of estrogen tremendously. Increased estrogen levels decrease the opportunity for eggs to implant. Thereby leading to a decreased chance of pregnancy and birth.