With blastocyst transfer, embryos remain in culture in the lab are
allowed to grow until they reach the blastocyst stage of development;
this generally occurs in about five or six days. This procedure is most
commonly performed when a patient has many excellent quality embryos
in an effort to select the embryo(s) to transfer that are most likely
to result in pregnancy. A disadvantage is that occasionally, some patients
will have no embryos that reach the blastocyst stage, and therefore,
no embryos to transfer.
Currently, our guidelines at AFS are to recommend the option of blastocyst
transfer to women who have a high risk of triplet or higher-order multiple
pregnancy or to couples who have a particular medical or social concern
about multiple pregnancy.