Once the embryo transfer has been carried out, it is most likely that there will be embryos left since in most countries only a transfer of a maximum of three embryos is allowed. However, it is increasingly common to opt for a single embryo transfer to avoid the risk of a multiple pregnancy.
Embryos left over from an IVF process can be frozen for use in future embryo transfers, either because the first attempt has not been successful or because the patient wants to have another baby. In addition, leftover embryos can be given to research or to other couples.
In any case, it will be necessary to fill out an informed consent form for these last two purposes.