George M Grunert MD, Reproductive Endocrinologist, HFS IVF Program Director

Reproductive Genetics

Couples thinking of starting or expanding their family should consider genetic disease carrier screening as an important step in their family planning process.

Carrier screening can help determine your risk of having a child with a serious genetic disease. A carrier is an individual who has one disease-causing variation in a gene. Most carriers do not have symptoms or a family history of disease and aren't aware of their carrier status. The majority of genetic diseases (like cystic fibrosis, sickle cell anemia, and Tay Sachs disease) are autosomal recessive disorders (AR), meaning that a child would have to inherit copies of the abnormal gene from both parents to have the disease. Some disorders (like hemophilia and Duchenne muscular dystrophy) are carried on the X-chromosome. These are called X-linked recessive diseases (XLR). XLR diseases can put malechildren at risk ifonly the mother is a carrier.Autosomal dominant (AD) diseases (like Huntington disease and Marfan syndrome), occur when onlyone copy of the gene is passed by either parent to the child. Negative carrier screening results do not completely eliminate the risk of having an affected child, but do indicate a significantly reduced risk.

Preimplantation Genetic Screening (PGS)

 

As women age, an increasing percentage of eggs have extra or missing chromosomes. An abnormal egg, when fertilized, results in an embryo with other than the normal complement of 46 chromosomes (called an aneuploid embryo). Aneuploid embryos rarely implant if transferred. Most aneuploid embryos that do implant, result in miscarriage. An exception to this is Down syndrome whichoccurs when the embryo has 3 copies of chromosome 21 (trisomy 21).

PGS (also called comprehensive Chromosomal Screening, CCS) is a technique whereby cells from the portion of the embryo destined to form the placenta are removed at the blastocyst stage for chromosome testing. This allows us to identify normal embryos for transfer. This has dramatically increased the chance of pregnancy at IVF, allowed us to transfer one embryo at a time (eSET), maintain outstanding pregnancy rates, and minimize the chance of multiple pregnancy.

Preimplantation Genetic Diagnosis (PGD)

If you are found to be a carrier of a genetic disease, either by family history or pre-pregnancy genetic carried testing, which puts your children at risk for serious medical complications,Preimplantation Genetic Diagnostic Testing (PGD) can be donein addition to PGS. This allows identification of affected embryos so that they can be excluded from transfer.

To arrange pre-pregnancy genetic carrier testing or learn more about PGS or PGD, please contact us or make an appointment for a consultation.

Houston Fertility Specialists Southwest Women’s Health Alliance