Following in vitro fertilisation (IVF), the embryos obtained are evaluated in the laboratory before transfer to the patient’s uterus. A key question always comes up at this point: which and how many of those embryos should be transferred?
The answer to this question must always be based on a search to obtain a balance between maximising the chances of pregnancy and minimising the risks associated with a multiple pregnancy (high blood pressure, an increased risk of diabetes, possible complications during childbirth, etc.) This decision is always taken on a personalised basis in each case and taking into account the conditions and the characteristics that are specific to each couple. For example, embryo evolution and development up until transfer.
Medical staff take into account aspects such as the female partner’s age, the cause of sterility, earlier attempts at IVF, the number of children the patient already has and any possible pathologies in the uterus. This information, along with embryo quality, is used to present the couple with a proposal and the couple makes the final decision.
Spanish legislation currently permits the transfer of a maximum of three embryos per cycle. However, progress in techniques and laboratory experience means that, on the whole, just one embryo of a good enough quality is transferred so that the chances of pregnancy are high without running the risks associated with a multiple pregnancy. The remaining good quality embryos are then cryopreserved and can be used in the future.