How Sex Selection Works:
Each genetic parent contributes half of a baby’s genetic make-up. The female is genetically an XX and therefore she can only contribute an X chromosome to the child. The male parent of the child is XY and can therefore contribute either an X or a Y chromosome to the child. When an X bearing sperm fertilizes an egg, a girl is conceived with the XX chromosomal make-up. When a Y bearing sperm fertilizes an egg, a boy is conceived with the XY chromosomal make-up. Typically, there is approximately a 50/50 chance of conceiving either a female or a male child.
Reasons for pursuing Sex Selection:
- Genetic Disease: Some couples have certain genetic diseases and do not want to pass these diseases on to their offspring. Muscular dystrophy and hemophilia are sex linked genetic disorders that affect male children so in order to avoid having a child afflicted by such diseases, some couples may choose to have a female child.
- Family Balancing: Families that already have a child or children of one sex may desire to have another child/children of the opposite sex. These couples can now turn to baby gender selection to fulfill their hope of having a family with offspring of both sexes.
There are also certain cultural, social and economic reasons for wanting to have a child of one specific gender.
Sex Selection Methods:
- Gradient Method: This method is the simplest sex selection technology. The sperm from the father is usually “washed” in the andrology laboratory and is then placed in a centrifuge which rapidly spins the sperm. As the sperm is spun, the centrifuge helps separate the X bearing sperm from the Y bearing sperm based on the weight of the genetic material. The X bearing sperm are heavier than the Y bearing sperm. This separated material can then be used for insemination into the female or can be used for IVF to create embryos to be put back into the female. The success rate of this method is not impressive and it is for this reason that at La Jolla IVF we do not recommend using this method alone.
- Flow Cytometry: This sperm sorting technique uses florescent dye to highlight sperm that carry X chromosomes. The X chromosomes pick up this dye because they contain more genetic material than the Y bearing sperm. A laser machine is then used to separate the two types of sperm. Again the sperm with the appropriate chromosomes is then used to perform IUI or IVF. Success rates with flow cytometry are about 60% to 70% of having a child of the desired sex.
- Preimplantation Genetic Diagnosis (PGD): This method is the only one that La Jolla IVF recommends because of its success rate of gender selection in San Diego. Over the past several years we have seen a marked increase in patients coming to us specifically for sex selection. Once they have made a decision of this magnitude they prefer to go ahead with PGD. We do not recommend doing PGD only for sex selection because once we are already performing an embryo biopsy on the embryos we think it is useful to obtain the aneuploidy testing as well. This testing can tell us whether an embryo is normal versus abnormal for certain chromosomal anomalies such as Down syndrome. This sex selection method entails the creation of embryos through IVF. Once the embryos are created they remain in the laboratory and the cells divide over a period of three days. On day 3 or 5, an embryo biopsy is performed where one cell is removed from the embryo and is fixed onto a slide which is then sent for DNA and cell structure analysis. The embryos remain in our IVF laboratory inside the incubator where they continue to grow from day 3 embryos to day 5 or 6 embryos. Early on day 5 or 6, our laboratory receives the results from the PGD laboratory as to which embryos are normal and what sex the embryos are. A decision can then be made regarding which embryos to transfer and which to freeze. Obviously, an embryo that is diagnosed as abnormal regardless of the sex would not be used for embryo transfer. The results with PGD are extremely successful and if a pregnancy is achieved there is a 99% – 100% chance of obtaining the desired gender.
In conclusion, the desire to increase the odds in favor of having either a female or a male child has been around since prehistoric times. Throughout the ages superstitions and old wives tales developed as to how to have a girl versus a boy or visa versa. Methods such as tying up one testicle, believing that boys came from one side and girls from the other, to sleeping with certain objects under the bed and even to having intercourse in different positions so as to try and achieve having one gender over the other developed. Today, for those families desiring a sure way of having one gender over the other, science has come of age with PGD “delivering the goods”. Sex selection is not without its critics however and it is not an inexpensive endeavor either but for those who wish to fulfill their hopes and dreams of having either a little girl or a little boy, now more than ever it is possible.