Single embryo transfer (SET) is when only one embryo is transferred during an IVF or FET (Frozen Embryo Transfer) cycle. This is the only way to greatly decrease the risk of multiples in pregnancy. It can also help to maintain a healthier pregnancy, as a multiple pregnancy carries greater health risks for both mother and babies.
In the past, multiple embryo transfer was frequently used in IVF treatment due to lower overall success rate. However, now that technology has greatly improved, single embryo transfer is just as successful and is looked to as the new best practice in IVF.