A study presented at the American Society of Reproductive Medicine Conference in Orlando last week, aimed to compare the safety and efficacy of embryo biopsies conducted for the purposes of screening for genetic disease at day 3 (cleavage stage) versus day 5 (blastocyst stage) of embryonic development. The impact that biopsy has on an embryo's ability to implant and develop into a baby had never previously been studied.

For twenty years, embryo biopsy for genetic disease screening prior to IVF transfer had been conducted on day 3, known as the cleavage stage, when only 6-8 cells have formed.. Day 3 biopsy involves removing 1-2 cells for testing. and removal of such a proportionately large percentage of the embryo reduces the embryo's chances of implantation.

More sophisticated techniques now allow biopsy on day 5, the blastocyst stage, when 200 or more cells are present.  The reason that day 5 biopsy does no apparent harm is that a dramatically smaller portion of the embryo is removed. Another reason is that the sample is taken from the outer layer of the embryo destined to form the placenta, called the trophectoderm (TE). The cells that form the baby are undisturbed, preserving the embryo's true potential.

Another advantage to the Day 5 biopsy is that a number of cells can be evaluated, reducing the chance for an error when one cell of an eight cell embryo may not reflect the remainder of the cells in an embryo, a phenomenon called mosaicism.

At Reproductive Partners we have been performing Day 5 biopsies for some time and find that it is a real advantage over Day 3 biopsies,