Gender Selection in IVF: What Is Its Place?

Gender Selection in IVF: What Is Its Place?

Couples have for centuries sought to influence the gender of their offspring. More than seven centuries ago the ancient Chinese developed a birth calendar said to be able to predict gender on the basis of when conception occurred. Later, the ancient Greeks suggested that by lying on her right side during intercourse, a woman could improve the likelihood of having a male child. And 300 years ago, the French suggested that placing a ligature around the right testicle would improve the chance of having a male child.

More recently in the U.S., methods such as timing intercourse, assuming different positions during sex, and (relatively recently) employing rapid sperm centrifugation in an attempt to separate male chromosome-bearing sperm from female sperm prior to artificial insemination were proposed. The fact is that none of these (as well as many other) such anecdotal assertions have been shown to have any real validity.

Currently, in spite of several well described medical approaches, the indisputable fact has emerged that it is only by way of IVF that reliable sex selection can be achieved. This allows for embryos to be screened for gender through preimplantation genetic diagnosis prior to transferring the embryo(s) of the desired gender to the uterus.

Nevertheless, it is an inescapable reality that the very idea of medical sex selection challenges moral and ethical beliefs at their very foundation. Many hold that the growing popularity of gender selection solely for the convenience of altering a family’s gender balance represents an unwanted example of how assisted reproductive technology is subject to abuse…and thus it should be outlawed. They also see it as an example of a disturbing trend towards “designer babies” where genetic engineering could be used to manipulate the intellect, body configuration, build, height, and the talents of future offspring. This assertion is commonly followed by the tantalizing question as to where all this would end and whether we as a society “would really want to live in such a world.”

There is, however, one clear exception to the apparent across-the-board opposition to sex selection that is well worthy of mention. This applies in cases where sex selection is used to avoid the occurrence of a serious medical disorder that selectively affects one gender or the other (e.g., Hemophilia, a life threatening bleeding disorder that selectively affects male offspring).

EVALUATING CURRENTLY USED METHODS FOR SEX SELECTION

Sperm Gradient Method (highly unreliable)

This is one of the simplest methods that still (unfortunately) remains in widespread use. Here sperm is rapidly spun down (centrifuged) in the hope of separating the male sperm (those with Y-chromosomes) from the female sperm (those with X-chromosomes). It relies on the assumption that the X chromosome makes sperm heavier, allowing for separation of male from female chromosome-bearing sperm. Though this method is often touted as a low cost method for sex selection, the truth is that it simply does not work!

Flow Cytometry-The Microsort Technique (has certain problems)

This method employs the use of a fluorescent dye that adheres to genetic material within the sperm. Because X-bearing sperm contain more genetic material, these sperm are supposed to pick up more dye than Y-bearing sperm. Thereupon, X and Y bearing sperm are then separated into two groups and used for intrauterine insemination (IUI) or IVF. This method has been touted as yielding a 60% to 70% accuracy rate with IUI. Some swear by this method, but my personal experience with its efficacy and reliability in the IVF setting has been rather disappointing. Significant to note is that approval of the Microsort method is still under review by the FDA and in the meantime, has only been granted approval for use in cases where it is necessary to prevent sex-linked or sex-limited genetic diseases in children.

Preimplantation Genetic Diagnosis (PGD)

Preimplantation Genetic Diagnosis is the only approach that offers virtually a 100% chance of obtaining the desired gender. In PGD, one cell is removed from each “potentially competent” early embryo, and then DNA based genetic analysis is performed in highly-specialized laboratories. We recommend comparative genomic hybridization (CGH) using paternal/maternal controls (GSN) in such cases because it not only determines gender but also helps identify the most “competent” embryos (those that have the proper number of chromosomes) and thereby significantly enhances success per embryo transferred. CGH has all but replaced fluorescence in-situ-hybridization (FISH) for PGD because, while the latter accurately can determine gender, it lacks sufficient sensitivity/specificity to optimally identify competent embryos for transfer.

Upon completion of the GSN-CGH analysis, which takes about 24-36 hours, the couple can select which embryo(s) they will transfer to the uterus. If pregnancy results, there is almost a 100% chance it will result in the desired gender. This method is particularly helpful for couples where the risk of having a male child with an X-linked genetic disease is significant.

A Personal Opinion On the Use of Sex Selection for “Family Balancing” 

Sex selection done simply for family balancing remains controversial, raising concern that if it became widely accessible and freely available, such practice could distort the natural sex ratio, leading to a population gender imbalance. However, for this to happen, there would have to be a significant population preference for sex selection. In reality, the contrary seems to apply, since studies conducted in western societies discount these concerns. In fact, the relatively high cost of IVF with the added cost of gender selection in the United States makes it unlikely that the demand would ever become large enough to impact overall population gender balance. In addition, several studies done in Western countries have shown that the majority of people do not seem to be concerned about the gender of their offspring, and that with a few notable exceptions, gender preference does not appear to be slanted in the direction of either male or female. Thus, from a practical standpoint, such concerns are overstated.

So, given that in the United States most do not care about the sex of their offspring, and only a minority are interested in selecting the sex of their children, it is my opinion that freedom of choice should prevail. As such, a service for sex selection for non-medical reasons should be freely available.

By Dr. Geoffrey Sher, MD

Gender Selection in IVF: What Is Its Place?, 5.0 out of 5 based on 1 rating