At some clinics embryo transfer following IVF takes place three days after fertilisation when the embryo contains around six to eight cells.
However, results from IVF clinics around the world suggest that pregnancy rates are greatly improved if embryos are left in the incubator to develop to their blastocyst stage which is usually by five days old. A blastocyst has many more cells than an embryo and, because of its longer development, may well be more viable for transfer and pregnancy.
At Medfem we generally prefer to transfer five day blastocysts as this give you the optimal chance of pregnancy. Once fertilised, eggs are left to develop to the blastocyst stage in culture medium in an incubator, and during this time they are checked for growth, shape and composition. Following this process allows the embryos to develop as closely to nature as possible – in a natural pregnancy it is a blastocyst, not the three day old embryo, which implants in the uterus.
Embryo monitoring and assessment allows our embryologists to determine whether a three day old embryo transfer or a five day old blastocyst transfer is more suitable.