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Blastocyst Transfer & Culture

Blastocyst Transfer

Blastocyst culture and transfer is a new and important technique that has been developed for in vitro fertilisation.  The procedure maximises pregnancy rates whilst minimising the risk of multiple pregnancies.

Traditionally embryos are transferred on the third day after egg collection, when the embryos are at the initial stages of cell division. Until recently, however, embryo transfer has been a compromise between maximising the degree of embryonic development, which can differ with each embryo, whilst minimising the exposure of the embryos to the culture media which, in the past, could only sustain growth for two to three days.

With the development of new media culture, if several good quality embryos are available on day three, couples now have the possibility of opting for transfer on day five. The embryos are allowed to grow in the laboratory until they are five days old at which time the cells of the embryo should have divided many times over and have begun to differentiate to form the foetus and the placenta. Embryos that survive to this stage of development are usually strong, healthy and robust and are now called blastocysts.

The inner mass of cells which are going to form the baby fuse together at the side of the embryo and the remaining cells go towards forming the placenta. The embryo has been allowed to develop into a more advanced structure which allows the clinician to determine more accurately which of the embryos have the most potential for successful implantation and a successful pregnancy.

Less than one in twenty women miscarry after a blastocyst transfer compared to about one in five women when the embryos are transferred at day three. A single embryo transfer, using a blastocyst, will also lessen the risk of couples having a multiple birth.

Ultrasound Guided Embryo Transfer

Three days after fertilisation an egg has divided into 6 to 10 cells.  By day 5 or 6 the embryos has divided into more than 16 cells and “hatches” into a blastocyst.

The image (above right) shows a 6-day old embryo that is in the process of “hatching” into a blastocyst ready for placing into the uterus using ultrasound guided embryo transfer. This can improve the implantation rates from 25% to 35%.

After retrieval and fertilisation, embryos are transferred after the 3-day culture period or 5 days when the embryo becomes a blastocyst.  The ultrasound scan  (picture opposite) shows the outline of the uterus and the flexible catheter releasing an embryo (not to scale) into the womb.  Blastocyst transfer can also improve implantation success as well as minimise multiple pregnancies.