The number of embryos to be transferred should be reduced to avoid multiple pregnancies while maximizing the pregnancy rates
In IVF cycles the number of embryos placed in the uterus is under the control of the couple and their physicians. Transfer of two embryos into the uterus result in a twin pregnancy rate of about 25 to 30%, versus less than 1% if one embryo is transferred. Single embryo transfer is associated with marked reduction in multiple pregnancies. The pregnancy rates after transfer of one embryo is lower than (2/3) that following two- embryo transfer. If pregnancy does not occur after single embryo transfer, an embryo is thawed and transfer to the uterus next cycle. The chance of achieving pregnancy using this approach (1+1) equals that of transfer of two embryos in the fresh cycle wile almost eliminating high order multiple pregnancies and markedly reduce twins.
We individualize the number of embryos based on age, morphology and stage of embryo transfer (day 3 or day 5 embryos) with one or two embryos transferred in younger patients with good embryo quality. Our team sits with the couple and discusses in details the chance for pregnancy in relation to the number of embryos transferred as well as the incidence of multiple pregnancies. We also discuss their aspirations and acceptance for fetal reduction.
In women 35 year or younger with multiple embryos available for transfer on day 3 we extend the culture to blastocyst stage to improve the ability to select the embryos with better potential for implantation. We also offer these women the chance to transfer one embryo and freeze the other embryo rather than transferring two embryos to reduce the chance for twins. If pregnancy does not take place, the frozen embryo is thawed and transferred. This approach yield chances for pregnancy comparable to transferring two embryos while markedly reducing twins.
Our ability to perform chromosome analysis for embryos enables us to select the embryo that will most likely lead to a pregnancy and a delivery. This permits the selection of a single embryo for transfer.