On average, about 30-50% of fertilized eggs will make it to the blastocyst stage. However, the percentage can vary depending on factors such as the female partners age and the particular IVF cycle she has undergone. At RMA New Jersey, which has one of the best embryology labs in the country, about 80% of eggs will fertilize, and of those, about 30-50% will make it to the blastocyst stage. Its important to note that the percentage of an egg or embryos survival at each stage is based on the preceding number, not the original number. In general, the younger the woman, the more of her fertilized eggs will reach blastulation, and the older the woman, the fewer. Its also worth noting that not all eggs will create healthy embryos, and the failure of some embryos to make it to the blastocyst stage is most likely due to a defect in the embryo.