For many people, the dream of having a family also includes the dream of having children of both sex. Since most families today are much smaller than in generations past, the odds of having two or three or even four children of the same sex is fairly high.

Throughout human history, there always has been interest in methods to sway the chances of conceiving a child of a particular sex. Today, in the 21 st century, it is quite clear that many of these sometimes bizarre and sometimes simple home remedies have no basis in fact.

There are ways to significantly shift the odds of having a child of one sex or another. Sex is conferred on an embryo by whether an X-bearing sperm (for a girl) or a Y-bearing sperm (for a boy) enters the egg. Unfortunately, despite highly publicized claims, there are no proven effective “at home” methods of sperm separation. Nor does timing of intercourse relative to ovulation affect the 50:50 sex ratio. By natural methods, the ratio remains a flip of the coin.

The only commercially available method for sperm separation that appears to be effective is the sperm sorting process available through Microsort.net. This method involves using a fluorescent DNA dye that attaches to either X or Y chromosomes. The sperm then passes through a cell sorter that separates the sperm based on the fluorescence. This method is still under FDA investigation for safety and efficacy but does appear to do a reasonable job in separating sperm, especially if the desired sex is female.

Mirosort reports a 90% success rate with separating X-bearing sperm and a 73% success rate in separating Y-bearing sperm. There have been only a few hundred babies born thus far, but there does not appear to be any increase in birth defects. Because this process is still considered “experimental,” couples wishing to participate, will have to travel to either Fairfax, Virginia (Microsort headquarters) or an affiliated clinic in Southern California for fresh sperm insemination.

Unfortunately, after Microsort processing, the number of sperm available for insemination is severely decreased. Freezing and thawing of sperm, which would allow the sample to be shipped to another location, reduces these numbers even further. Because sperm counts are so low after sorting, it is usually necessary to do in vitro fertilization with sperm injection (IVF-ICSI) to significantly improve the fertilization in the IVF laboratory. PFC is a participating site in the FDA investigation for Microsort. We have used sperm specimens that had been previously Micro-sorted for IVF-ICSI.

Researchers at UC Irvine recently published a study describing the use of lasers to “trap” the heavier and slower moving X-bearing sperm to separate it from the lighter Y-bearing sperm. In the future, this process may provide an alternative to Microsort. However, it is not yet commercially available.

Beyond the Microsort technique, the only way to improve the odds of selecting one sex over another at close to 100% accuracy is to undergo Pre-Implantation Genetic Screening (PGS). PGS uses a DNA-binding technique to determine if there are a correct number of chromosomes in the embryo at the time of IVF. To complete this screening, embryos on Day 3 of culture (5-10 cells) undergo a biopsy to remove a single cell. The rest of the embryo remains in culture in the IVF laboratory. The removed cells are analyzed for the correct number of chromosomes. Currently, PFC with its cytogenetic partner, Genetics and IVF Institue screen embryos for 3-12 chromosomes. This screening is called “aneuploidy screening.” We allow our patients to know and select the sex of their normal embryos for transfer if they so wish.

Although IVF with PGS is the most effective method for sex selection, it is certainly the most expensive and there is no absolute guarantee that the transfer of the screened embryos will result in pregnancy. A PFC physician can best discuss the odds of success, based on the woman’s age and the couple’s history of childbirth.

Many couples undergoing PGS are doing so to screen for specific genetic defects or are specifically undergoing sex selection because of their risks of having a genetic disease that only affects males (X-linked diseases).

On the other hand, PGS for elective sex selection, either for “family balancing” or even for having a first child of a particular sex poses difficult ethical issues. Just because we have the ability to choose the sex of a child, should we? What will the couple do with normal embryos of the undesired sex? At PFC, we do not encourage PGS for elective sex selection. However, if a couple is undergoing IVF and wishes to undergo aneuploidy screening, we do allow them to select to transfer embryos by sex. We encourage all patients to consider donating excess embryos of the undesired sex for adoption by other couples.

Women or couples interested in this procedure should discuss it with their Reproductive Endocrinologist. At PFC, we also refer our PGS patients for a special genetic counseling session at California Pacific Medical Center in preparation for this process.

Tags: ICSI, IVF - In Vitro Fertilization, PGD - Preimplantation Genetic Diagnosis, PGS - Preimplantation Genetic Screening, Treatment Options

This entry was posted on Sunday, February 10th, 2008 at 3:48 pm and is filed under From Us To You. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.