Choosing Your Baby's Sex

PGD involves screening the embryos created during an IVF cycle BEFORE they are returned to the uterus. A single cell is removed from the embryo and the genetic material is examined to screen for abnormalities. Particularly useful for couples with a known history of genetic disease, this early screening of embryos allows only embryos without known genetic defects to be returned to the uterus. Some of the diseases which may be screened out with this procedure include Downs Syndrome (Trisomy 21), Cri du Chat (Trisomy 18), Tay Sachs disease, Huntington's disease and cystic fibrosis as well as many X-linked diseases. PGD may also be used to look for chromosomal aberrations as an explanation for repeated miscarriage and/or failed previous IVF cycles.

After three days in culture the embryos typically reach the 8-cell stage. One to two cells are removed from each embryo on day 3 and analyzed by one of the techniques described below:

(A) Testing for the genetic mutation is performed only on cell(s) removed from each embryo.  The cells are tested by a very powerful technique called fluorescent polymerase chain reaction (F-PCR) that has the capacity to make millions of copies of the piece of DNA of interest so that a reliable diagnosis can be made on each embryo. The product from the F-PCR reaction is then tested for the presence or absence of the known parental mutation(s) using a range of genetic techniques. Currently this testing is performed at the laboratory of Dr. Mark Hughes at Genesis Genetics Institute.

(B) For examining chromosomal defects the cells are analyzed using a technique call fluorescence in-situ hybridization or FISH.  This technique uses probes, small pieces of DNA that match the chromosomes of interest to study the cell’s chromosomal make-up.  Each probe is labeled with a different fluorescent dye.  These fluorescent probes are applied to the cell and attached to the chromosomes.  Under a fluorescent microscope, the geneticist counts the chromosomes, and, for translocation cases, can distinguish normal cells from cells with an unbalanced translocation. 

Some doctors analyze an embryo’s DNA so parents can choose to have a male or female placed in the womb. Last year, a survey found that 1 of every 11 Pre-Implantation Genetic Diagnosis treatments was for sex-selection alone. The study by Johns Hopkins University also found that 42 percent of clinics offering PGD offer it for sex selection.

 

More info on:

• Los Angeles Fertilization Services
• In Vitro Fertilization Procedures
• Ovulation Induction