A very nice IVF patient from Tampa had very good questions this am when I saw her for her baseline ultrasound visit. She is only 32 and has requested that we do PGS to screen her IVF blastocyst for chromosomal problems. She also thought that the PGS would screen for all types of muscular dystrophy as her husband’s diseased grandfather had a type of late onset “muscular disorder” that no other relatives have encountered. She had a thorough pre-preconception genetic screening with Counsyl Genetics, but her husband declined testing.
I explained that the PGS with 24 chromosome complete genomic hybridization with microarray technology will tell us if the embryos the embryos have a balanced and correct number of chromosomes within the limit of the test and the fact that we are sampling the trophectoderm of the blastocyst and not the inner cell mass that becomes the baby. Just because we have a normal result for PGS does not mean that the embryo and the subsequent baby is “guaranteed” to be free of a disease or affliction. PGD or the testing of embryos for known diseases is available when we know what the disease is and are actually testing for it.
(The trophectoderm is seen from 5:30 to 11:00 o’clock while the inner cell mass is the group of cells @ 2:00 o’clock)
For example, recently we had a patient that is a known carrier for Spinal Muscular Atrophy. We treated her with both PGD and PGS. The PGD tested the embryos for the particular know carrier disease while the PGS then checked that the embryos had normal numbers of chromosomes. Some embryos were afflicted with SMA while others were carriers and others were free of the mutation. Some embryos that were free of the SMA problem were found to have chromosome imbalances that would have resulted in an abnormal baby or a miscarriage.
Please review this information in our web site at www.geneticsandfertility.com
All The Best!
Julio E. Pabon, M.D., F.A.C.O.G