Sex Selection

Sex selection, also known as gender selection may be performed for medical reasons to avoid sex-linked diseases such as hemophilia and Duchenne’s muscular dystrophy, and is an acceptable means of avoiding debilitating diseases in one’s offspring. Gender selection for family balancing purposes is also available for some families.

Methods of gender selection:

There are a several methods of sex selection procedures available to couples seekig such treatment. However, there are only two pre-implantation methods that have proven to be reliable and successful in selecting the gender of choice. The first is known as pre-implantation genetics diagnosis (PGD) and the second is known as MicroSort sperm separation. While there are other methods that purport to increase the chances of one sex or the other, the above two methods PGD& MicroSort) are the only ones that have held up to scientific testing.

Pre-implantation Genetic Diagnosis (PGD)

Perhaps the most accurate method of gender selection is through pre-implantation genetic diagnosis (PGD) using fluorescent in situ hybridization (FISH) or polymerase chain reaction (PCR) technologies. While PGD is the most reliable method, it does involve undergoing an assisted reproductive technology cycle known as IVF (in vitro fertilization). In a PGD cycle for sex selection embryos are grown in the laboratory for approximately three days until they reach the 6-10 cell stage of development. Using specialized microscopes and highly skilled technicians a single cell is removed from each embryo and “fixed” to a sterile microscope slide. Each cell on the slide is numbered and corresponds to the embryo from which it was removed. The slide containing the fixed cells is sent to a professional PGD testing laboratory where the FISH testing is performed on each cell. At this laboratory the trained technicians are able to identify which cells contain two “X” chromosomes (female sex) or one “X” and one “Y” chromosome (male sex). His information is sent back to the A.R.T. center and the sex of each embryo is now known. If the couple desire only female embryos be transferred back into the uterus this can now be done, and the same if only male embryos are preferred. The accuracy of this testing is around 98%!

Separation of sperm

At conception the sex of a baby is determined by whether a “X” or “Y” bearing sperm fertilizes the egg. Separation of X and Y bearing sperm from is possible as the “X” chromosome is larger than the “Y” chromosome. As both these chromosomes are made up of DNA and the X chromosome contains over 25% more DNA than a Y chromosome this difference can be taken advantage of to separate the two types of sperm. MicroSort® is a technology that has been developed to separate the two types of sperm from one another in a semen sample based on the difference in the amount of DNA in the two sperm cell types. By using a specialized instrument known as a flow cytometer, the small difference in DNA weight between X and Y sperm can be measured and used to sort the two sperm cell types into different channels of the instrument. After the semen specimen has been sorted the purity of each separated sample is determined by FISH (fluorescence in situ hybridization) using a small portion of the sorted sample. The DNA probes that are used to make the determination specifically attach to either the X or Y chromosome in sperm and emit either a red/pink or green color for X-bearing and Y-bearing sperm, respectively. The Microsort® process yields an accuracy rate of over 90% for X chromosomes, and over 80% for Y chromosome. The specimens are frozen and sent back to the A.R.T. center to be used for an IVF/ICSI procedure.