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Gender Selection: What You Need to Know
a blog by David Tourgeman, M.D., HRC Fertility, August 11, 2011
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For now thousands of years, couples have unsuccessfully tried to influence the gender of their future babies. Not until recently have there been developments in the reproductive field that have actually been able to successfully yield the desired gender of a baby.
Historical Attempts at Gender Selection
Dating back to the time of ancient civilizations, early Greeks believed that tying off the left testicle during intercourse produced a higher likelihood of conceiving a male gestation, while tying off the right testicle was believed to increase the odds of producing a female. In the Jewish religious tradition, it is written in the Talmud that the woman should have an orgasm before the man if trying to achieve a male gestation, and vice versa for a female gestation. Similarly, ancient Chinese astrologic forecasts utilize the lunar month of conception for predicting the desired gender.
Unfortunately, none of these methods have been effective in dictating which gender will be conceived.
Modern Attempts at Gender Selection
In more recent years, couples have sought to increase the odds of a particular gender at home. It is known that sperm is what dictates gender — if an X chromosome fertilizes the egg, a girl is conceived, and if a Y chromosome fertilizes the egg, a boy is conceived. Thus many methods have been used to alter the concentration of desired sperm.
There are gender selection diets and herbal supplements. Also very popular is timing intercourse around the time of ovulation. Similarly depth of penetration or sexual positioning have been felt to sway the odds. The “turkey baster method” or home cold remedies have been used to change the vaginal pH level or the cervical mucus. Many of these at-home methods are based on the supposition that the Y-bearing sperm swim faster and prefer an alkaline environment. Conversely, it is supposed that the X-bearing sperm tend to swim slower, last longer and prefer an acidic environment.
Thus, in theory, increasing the fluids should help tip the odds toward making baby boys. Some wishing for boys take cold medicines such as Benadryl to increase the cervical fluids and help usher the Y-bearing sperm upstream. Other options, including drinking lots of water or grapefruit juice and avoiding caffeine are also popular. On the other hand, women who want baby girls try to do the opposite, that is, dehydrate their cervical mucus. This has included the ingestion of expectorants, decongestants, vitamin C, caffeine and even Clomid. Nutritional and herbal supplements have also been attempted. Supplements such as cranberry tablets, calcium, magnesium and vitamin D are supposedly recommended for the conception of a baby girl, whereas supplements such as potassium, sodium and caffeine are supposedly recommended for the conception of a baby boy.
As it turns out, nature’s odds remain pretty close to being 50/50, regardless what is done at home.
Early Scientific Proposals
There was some early scientific work that has not proved fruitful either. The Shettles method is very popular — it is based on the fact that the Y-bearing sperm swim faster, but do not live as long as the X-bearing sperm. It also assumes that the vagina is mostly acidic, but becomes more alkaline close to the time of ovulation. Thus, the Shettles method advises that to conceive a boy, intercourse should occur on the day of ovulation or the day before, whereas in order to conceive a girl, intercourse should occur two to three days before ovulation. It has also been recommended that if a boy is desired, female orgasm should occur, as this alkalizes the vagina. Unfortunately, the odds of this working in a couple’s particular favor remains 50/50.
The Erickson method, or “sperm spinning” is based on the fact that the X chromosome is larger than the Y chromosome; it follows that the X chromosome should be heavier. When placed into a protein gradient, the heavier sperm should sink, and the Y chromosome should stay on the top. As the DNA difference turns out to be a change of only 2.8 percent, the overall weight difference of the X and Y-bearing sperm is negligible. Thus this separation method unfortunately is not fruitful in determining a particular gender.
Effective Tools for Gender Selection
A newer scientific method that has been utilized with some success is the MicroSort sperm preparation. This method of sperm separation utilizes a fluorescent dye that temporarily binds to the DNA of the X and Y chromosome. The absorption of the dye depends on how much DNA there is, which in turn will determine which chromosome will be sorted through the flow cytometer. It is a little less likely to yield a boy simply because the binding on the chromosome is less efficient, yielding an accuracy of 73 percent, whereas for an X-bearing chromosome, the accuracy is 88 percent.
At this point, the device is being utilized solely for sex-linked diseases. For example, hemophilia is an X-linked disease, thus one would want to avoid a male offspring, which only has one X chromosome. At this time, MicroSort is not used for family balancing, but rather in cases in which there is a predisposition to X-linked diseases.
The only effective tool for family balancing is pre-implantation genetic diagnosis (PGD), which fortunately yields an efficacy in selecting a desired gender of 99 percent. In order to achieve this, in-vitro fertilization (IVF) is necessary. On the third day of growth of the embryos, one cell is removed and sent for evaluation.
There are two ways in which gender can be established. The cell may undergo a technique called fluorescent in-situ hybridization, which is able to delineate either male or female gender. Another technology can also be used to evaluate all 23 pairs of chromosomes via a technique called single nucleotide polymorphism. In this way, healthy boy or girls embryos are identified.
Once the testing has been performed the embryo(s) of the desired gender are replaced into the mother’s uterus. Despite the significant amount of effort that is required, after thousands of years of trying to influence gender outcome, we finally have a technique that works!
David Tourgeman, M.D. graduated medical school from the University of Southern California in 1994. He completed his residency in Obstetrics and Gynecology in 1998 and his fellowship in the Division of Reproductive Endocrinology and Infertility in 2001 at the University of Southern California, Los Angeles County Women’s and Children’s Hospital. After his fellowship, Dr. Tourgeman became an assistant professor of Obstetrics and Gynecology in USC's Division of Reproductive Endocrinology and Infertility. He began working with HRC Fertility (then Huntington Reproductive Center) in 2005 and currently sees patients in HRC’s Encino and West Los Angeles offices. His areas of interest and studies include assisted reproductive technologies and oocyte donation in women of advanced reproductive age, alternatives for enhancing embryo implantation, advanced reproductive fertility surgery, evaluation of ovulation induction agents, and vaginal hormone administration.