A fertility clinic will present the success rate for both Woman A and Woman B as 100%, i.e. both women had one embryo transfer procedure and both women went on to have a single baby.
The HFEA (the UK’s fertility regulator) now asks fertility clinics for the success rates “…per embryo transferred”. So in our example, the success rates for Woman A remains the same, i.e:
Women A has a single embryo transferred to her in a single embryo transfer procedure and goes on to give birth to a single baby. The success rate is 100%
For Woman B, however:
Woman B has 2 embryos transferred to her in a single embryo transfer procedure and goes on to give birth to a single baby. So, the success rate per embryo transferred is 50% (the number of births divided by the number of embryos transferred).
Both methods of calculating the success rate are correct, but it’s important to be clear how the success rate for embryo transfer is being calculated.
Gynii Me supports the HFEA’s recommendation, that transferring one embryo at a time, is often the safest option of securing a live birth. However, a patient’s individual requirements may mean that there are obvious medical benefits to transferring two embryos at the same time. For example, a patient who is over 40, with fewer opportunities for further IVF cycles, may have two embryos transferred in a single treatment procedure.