The egg-to-baby pipeline
Not every frozen egg results in a live birth. Each stage of the process has its own success rate, and the rates compound. Typically: ~85% of eggs survive the thaw, ~75% fertilise, ~50% develop to blastocyst stage, and ~30–40% of blastocysts implant.
Age is the single most important factor. Eggs frozen before age 35 have substantially higher success rates per egg than those frozen at 38–40 or beyond. The calculator uses published age-group data to estimate how many eggs would be needed for a given number of desired live births.