Figure 1. Potential range of preimplantation loss among 100 unselected couples in their first-cycle attempt of pregnancy. We assume that 36% of couple will have an implanting pregnancy and 24% of couples will have a live birth. We also take into account cycles where no fertilization is possible due to sterility, anovulation or mis-timed intercourse (14%), leaving 86 couples (or cycles) as the denominator for possible preimplantation loss.