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Cell sorting



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Sex Selection

Throughout history couples have wanted to be able to select the sex of their unborn child. Recent surveys in America show that couples interested in sex selection are interested in it primarily to balance the sex of children in their family. Couples wish to experience the excitement of raising both a boy and a girl child.

Throughout time there have been many approaches to sex selection. Until recently, these have been based on either simple-minded or sexist approaches to sperm. My favorite technique in the history of this subject is based on the belief that boy sperm originated in the right testicle and girl sperm originated in the left testicle. This belief persisted for hundreds of years. If one wanted a boy child, all that one would have to do is to tie off the left testicle.

In the 1950's there were books that were very popular in describing how to select a particular sex for your child with prescriptions for the how, why and when of intercourse. More recent approaches have utilized sperm processing. The basis for some of these approaches was the belief that boy sperm (being intrinsically superior) swim faster than girl sperm. Millions of dollars have been spent by patients to obtain some of these sperm processing techniques.

With sophisticated DNA testing it is clear that none of these older techniques are actually able to differentiate boy, or Y chromosome containing sperm and girl, or X chromosome containing sperm. The difference in mass of an X and Y sperm is approximately 3%. There are both subtle and non-subtle differences in the shape of sperm not related to the sex of the sperm. These significantly effect both the volume of the sperm and the way that that sperm swims much more than a small difference in mass. Although controlled trials for sperm selection have always been a study that medicine is capable of doing, to my knowledge no one has ever undertaken a truly controlled trial in this setting.

Cell sorting with flow cytometry

There is now one technique that has been shown to be effective in selecting X and Y bearing sperm. The technique uses a fluorescent stain on the sperm and the sperm are separated using a flow cytometer (sometimes referred to as a cell sorter). This technique of cell sorting is available through IVF And Genetics Institute in Fairfax, Virginia (703-876-3897). It is still an experimental procedure, but preliminary data suggests that it is particularly good at selecting X bearing, or female, sperm. Unfortunately, because of technical reasons even if one is starting with a very good specimen, only a few sperm are able to be selected. Because of the small number of sperm selected the variant of IVF known as ICSI, where sperm are injected directly into eggs, is required in order for pregnancy to be achieved.

This procedure can be performed at Infertility Solutions, P.C. using IVF And Genetics Institute to perform the sperm sorting procedure. The husband would produce a specimen for us here. We would freeze it and ship it to IVF And Genetics Institute. They would then re-freeze it and ship it back to us. We would then undertake ICSI and defrost the sperm that have been sorted, and use them in the procedure. The sorting procedure increases the cost of the IVF/ICSI procedure by about one-third. Since the procedure is still experimental, IVF And Genetics Institute has a separate consent form that would have to be signed by the couple requesting this procedure.


More recently another technique for sex selection has been clinically available, namely PGD. It's accuracy is theoretically 100%. PGD involves creating embryos with IVF, removing a cell from the embryo and testing that cell to see if it is from a male or female embryo. Embryos of the desired sex can then be transferred. Although adds cost to that of a routine IVF cycle, since only a few few chromosomes need to be looked at, the additional cost is relatively low.

One problem created by this type of sex selection is what to do with the presumably normal embryos of the wrong sex. We certainly have patients who would be thrilled to have them donated to them. Some of our sex selection patients freeze all their unused embryos with a plan to decide what to do with them at a later time.