SET (Single Embryo Transfer)
The great goal of all IVF clinics is to reduce the amount of twin and particularly triplet pregnancies, as they are high risk. The Australian NHS (National Healthy Service) also expressed particular concern regarding the costs involved and urged IVF clinics to avoid them.
In the early days of IVF, transferring at least two embryos was the norm. This, however, had little effect on pregnancy rates.
Ongoing research and development, on the other hand, has increased pregnancy rates. Improved medication, better knowledge and experience in reproductive medicine and, in particular, improved laboratory culture conditions have enhanced the selection process of embryos before transfer.
The embryo deemed to have the best chances is selected according to developmental and morphological criteria. Blastocyst cultures, which are legal in Austria, improve the selection process.
But it is also important to note that freezing surplus embryos with good morphology is just as likely to lead to a sustainable pregnancy.
If the transfer using a fresh embryo is not successful, it is almost always using a cryo-embryo. The pregnancy rate of fresh and cryopreserved embryos is called "cumulative" pregnancy rate. This rate is comparable with (if not higher) than the pregnancy rate derived from the transfer of two fresh embryos. However, in this case it is likely that both embryos lead to ongoing pregnancies.
The disadvantage of SET is the increased time it takes to get pregnant, as a cryo-cycle is also performed.
But a single pregnancy takes the burden of mother and child reduces the risks associated with multiple pregnancies.