“The main difference between freezing eggs and freezing embryos: ‘whether the eggs are fertilized before or after they’re frozen and thawed,’ says Josh Klein, M.D., co-founder and reproductive endocrinologist at Extend Fertility. When freezing embryos, you need to know the intended father, since his sperm fertilizes the eggs before freezing. On the other hand, you can freeze eggs without sperm (they’ll be fertilized once you undergo IVF). Freezing embryos also lets you know how many eggs were healthy enough to survive fertilization, says Dr. Klein.”