Gender Selection
Gender Selection or Family Balancing
Many of us know someone who would desperately like to have a girl or a boy. Perhaps a couple has several children of one gender already and would like to have another child but would only consider doing so if the 50/50 odds could be shifted in favor of the other gender. This is sometimes referred to as “family balancing”. Or, perhaps a couple is seeking infertility treatment, already has one child, and would prefer that the next child is the opposite gender. This is quite common nowadays as families are smaller in size. Another couple may want to avoid passing one of the more than 500 gender-linked genetic diseases to their child, so they might consider using it PGD for gender selection.
Couples have sought to influence the gender of their children for hundreds of years. In ancient Greece, men believed that lying on their right side during intercourse increased the likelihood of a male child. A Chinese birth calendar buried over 700 years ago in a tomb outside Beijing is said to predict gender by when conception occurred. In 18th century France, men would tie off their right testicle to ‘guarantee’ having a boy. In modern day America other methods have been tested, such as timing of intercourse, certain sexual positions or placing live sperm on an albumin gradient. None of these methods has been shown to be scientifically valid.
When a sperm with a Y chromosome fertilizes an egg, it makes a boy. When an X chromosome bearing sperm fertilizes, it makes a girl. Any given sperm sample contains a roughly even (50/50) amount of X (female) and Y (male) bearing sperm. Research in animals has shown that it is possible to separate sperm using a technique known as DNA flow cytometry. The separation of male and female sperm is based on the measurable difference in the quantity of genetic material (DNA) they contain. The sperm absorbs a dye, which attaches temporarily to the DNA, or genetic material, inside the individual sperm. When exposed to laser light, the dye fluoresces. Since the X chromosome is larger than the Y, there is more DNA for the dye to attach to and, consequently, the sperm with the X chromosomes will fluoresce more brightly than those with Y chromosomes. The flow cytometer is able to pick up these differences in brightness and separate the sperm as they move through the machine one at a time. Other methods of sperm processing have been described using albumin gradients and the sperm are used for intra uterine insemination ( IUI). In such a procedure, the woman is monitored carefully to establish the time of ovulation. Some of this monitoring can occur with her local physician and/or the use of ovulation predictor kits, which can be used at home. Insemination is performed very close to the time of ovulation. On the day of ovulation the husband produces a sperm sample, the sperm are sorted for the desired gender, and the insemination with the sorted sperm occurs later that same day.
For patients who need additional assistance achieving pregnancy, or who seek to raise the odds of achieving a successful pregnancy, In Vitro Fertilization with biopsy of a resulting embryo has been shown to be effective and a reliable method of gender selection. Couples may decide that they want a method of gender selection that offers them an almost 100% chance of obtaining the desired gender. To accomplish this, IVF can be used in conjunction with embryo testing (Preimplantation Genetic Diagnosis or PGD) where only embryos of the preferred gender are placed back in the uterus. PGD is the testing process that can provide the answer. In PGD, one to two cells are removed from these early embryos, and then DNA based genetics analysis is performed in highly-specialized laboratories. Upon completion of the analysis which takes about 24 hours, couples can select which embryos they will use. If pregnancy results, there is almost a 100% chance it will be of 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.
Some frown upon the use of available medical and financial resources for gender selection, claiming it may distort the ratio of gender in society; it is too much interference with the natural process and so forth. So long as couples are willing to pay for the services themselves and not rely upon third party payers for reimbursement, these technologies should be made readily available to these couples. At our clinic, in any given year, we maintain a log book and try to keep requests for a specific gender at 50:50. In this way, we cannot be accused of interfering with nature’s balance in society. It is likely that the method of separating and selecting sperm will evolve in the future, making this science more reliable. However, even at the present time of using IVF with PGD for sexing each particular embryo and then only replacing those of “the desired” gender, this affords close to 100% certainty for desired sex.
Rev. 04/12
