PGD abnormal results

[lindi]

I have read that because one cell can sometimes not be representative of the actual embryo's cells due to mosaicism, there is a rate of error in PGD both ways- a normal embryo will be called abnormal and vice-versa. Is there any knowledge about how often this happens? And is it ever considered after a 3 day biopsy that returned abnormal results to do an additional PGD biopsy on the same embryo at day 5 if it makes it to blastocyst?

[Carole]

Hi Lindi,

Here's a link (http://www.inciid.org/printpage.php?cat=pgd&id=265) to a physician's summary of indications for PGD which includes an estimate of genetic mosaicism. In this physician's lab, they found genetic mosaicism rate of about 7%, which falls in line with what I have read elsewhere (10% or less). There are some scientific papers out there that suggest some types of genetic problems like Robertsonian translocations may have a higher frequency of mosaicism.

I have not heard of sampling an embryo on day 3 and repeat biopsy on day 5. In order to reduce the chance of misdiagnosis, programs either sample two cells on day 3 (but there are some reports that removing an extra cell on day 3 may sometimes decrease the pregnancy rate) OR labs are starting to do more trophectoderm biopsy of blastocyst stage embryos on day 5 because they can sample more cells and aren't taking any of the cells that contribute to the fetus. The only down side of trophectoderm biopsy is that you can't get test results back on the same day (day 5) so all biopsied blastocysts are frozen, pending test results, and a frozen embryo transfer cycle is scheduled, usually for the next month. Your IVF lab needs to be good at freezing blastocysts, usually by the vitrification method to get the most benefit from trophectoderm biopsy PGD. However, a later FET may have an upside too. There is a good bit of scientific evidence to suggest that implantation may be improved in a non-stim cycle, because the only drugs that are taken are to prepare the uterine lining for implantation. The high estradiol levels achieved in some stims may not be so great for implantation. In a subsequent FET cycle, you avoid that issue. Hope this helps. Carole

[lindi]

Thanks. I have 8 strong embryos at day 3, so my RE has counseled me to wait until day 5 for biopsy and freeze, ( they have fantastic FET stats) and I will be doing the FET the following month due to high estrogen at this point so my body can reset itself and be more favorable for implantation as you mention- he also cited the studies that show the increased success in using this method for my age group and hormonal make up. I do hope the day 5 biopsy will lessen the chance for inaccurate CGH results.

[Carole]

It sounds like you have a good start and a good plan for an FET!! Wishing you a BFP this cycle! Carole

[lindi]

Thanks!