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Good Day to All,

These past few blogs covering PGD raise a few important issues. There are some well-know fertility centers that are really pushing TE biopsy. The feeling is that the technology has finally become accurate and safe enough.  It may be that doing IVF with PGD leads to a higher pregnancy rate and a lower miscarriage rate.  Plus, if you know you are getting a normal embryo, we can transfer fewer embryos, lowering the rates of twins and triplets.

This all sounds good, however, I think we need just a little more time, but maybe not much more.  In a good center, the pregnancy rate for a woman under 37 years of age is 40-50% without PGD.  PGD adds an invasive procedure. The shell of then embryo has to be opened, usually by a laser beam, then some of the embryo, even if it’s a small piece, has to be chopped away.  We make it sound simple, and so far it seems safe, but no one should promise you all of the safety data is in.  Not to mention the additional costs, which could vary from program to program, but $6,000 is a safe estimate.

In theory, ideally, PGD will be the way to go and everyone doing IVF will have their embryos tested, the pregnancy rates will go up, miscarriage rates will go down and we will say goodbye to IVF twins.   And if the system works really well, in the end this will save money because people will need fewer IVF cycles for success (not to mention the drug cost savings if fewer cycles are needed).

Encouraging news concerning PGD is coming out of the data on miscarriage. Good PGD does decrease the rate of miscarriage. A very high percentage of miscarriages are caused by aneuploidy, which means an abnormality in the number of chromosomes present in the embryo. Just one example of aneuploidy is Down’s syndrome, which is the result of an extra chromosome 21 (also called trisomy 21).  The bulk of PGD is performed looking for aneuploidy.

The reduction of miscarriage rates after PGD has 2 important implications. One is that preventing a woman from having a miscarriage is obviously a welcome idea, as the emotional toll of pregnancy loss is significant. The second is that miscarriage takes time.  While many miscarriages occur early, many women do not suffer their loss until 7-10 weeks, later if the fetus survives to the CVS (10 weeks) or amnio (17 weeks).  When you add in the recovery time of 1-2 months before a woman can try again post-miscarriage, the total time lost could be 2-4 months. This is especially difficult in an older woman whose reproductive time is already limited.

One shortcoming of this technology is that this new method of testing requires a blastocyst. Many IVF programs are still not comfortable growing their embryos to blastocyst; they prefer transferring their embryos on day 3.  These programs will not be able to provide these new services until they become very good a growing embryos out to day 5, which for some clinics could take a very long time.

Lastly, not everyone who wants PGD is a candidate for PGD.  The group that may benefit the best from a PGD cycle is those who are above the average age for reproduction. However in this group, egg production is lower, as is the rate of good (biopsyable) blastocyst formation. So there may be the intention for PGD at cycle start, but if the egg number or embryos quality is low, the option for PGD in that cycle may be lost. Straight IVF may or may not still be a viable option, but at times even those are not possible.  I try to be positive to the end, but it is always necessary to cover all eventualities.

 

Well, that’s quite a bit about PGD. Thanks very much for reading.

Don’t forget to read the disclaimer from 5.17.06.

Dr. Licciardi

References:

  • Braude P. Preimplantation diagnosis for genetic susceptibility. N Engl J Med 2006; 355(6):541-3.
  • Gutiérrez-Mateo C., Colls P., Sánchez-García J., Escudero T., Prates R., Wells D., Munné S. Validation of microarray comparative genomic hybridization for comprehensive chromosome analysis of embryos. Fertil Steril. 2011; 95: 953-958.
  • Twisk M, Mastenbroek S, van Wely M, Heineman MJ, Van der Veen F, Repping S. Preimplantation genetic screening for abnormal number of chromosomes (aneuploidies) in in vitro fertilization or intracytoplasmic sperm injection. Cochrane Database Syst Rev 2006; 25(1):CD005291.
  • Munne S, Fischer J, Warner A, Chen S, Zouves C, Cohen J, Referring Centers PGD Group. Preimplantation genetic diagnosis significantly reduces pregnancy loss in infertile couples: a multicenter study. Fertil Steril. 2006; 85(2):326-32.