In AAFC, we can offer gender selection to couples that desire to have a son or a daughter. Additionally, we sometimes perform gender selection to minimize the risk of disseminating a genetic condition carried by one or both of the parents.
How is the gender of a prospective baby determined in a pregnancy?
In every cell of the human body, the genetic material (DNA) is organized in 46 strings of information called chromosomes or in 23 pairs of them with one copy coming from the maternal DNA and one from the paternal.
The gender of an embryo is determined by the sex chromosomes, X and Y. In all cells of the body, a woman always have two X chromosomes and a man always have one X and one Y chromosome. Egg and sperm cells, however, are an exception. They have half of the genetic material to the rest of the cells in the body carrying 23 unpaired chromosomes. This allows them to maintain the total number of chromosomes stable when they come together during fertilization. The newly created life will again have 23 chromosomal pairs (46 chromosomes in total) with half contribution from the mother and half from the father.
Hence, the eggs always have one X chromosome, and sperms can have either one X or one Y chromosome, being the sex-determining factor. When an X-bearing sperm is combined with an egg, they produce a baby girl (XX), and when a Y-bearing sperm is combined with an egg, they produce a baby boy (XY).
Who may benefit from gender selection?
Gender selection is a method of choice for couples that wish to have a son or a daughter for a number of social reasons. For instance, they may wish to balance their family, because they already have older son(s) or daughter(s).
But also, gender selection is extremely useful method for minimizing the risk of disseminating a genetic condition due to a mutation on the X chromosome of both or one of the parents.
For instance, in the case that a mutation is located on the X chromosome of the mother(X-linked genetic condition), this couple, with each pregnancy, may expect 50% chance of having baby boys that are completely affected by the condition, and 50% chance of having baby girls that are carriers of the condition. So, for these parents to have a healthy child, we can use gender selection and choose for the unaffected embryo of their choice, the non-carrier, completely healthy male or female embryo.
How is gender selection done?
We perform gender selection by the use of In-Vitro Fertilization (IVF) and Preimplantation Genetic Diagnosis (PGD) on the early, 8-cell stage embryos (3 days post-fertilization) or on the blastocyst stage(5 days post-fertilization).
Briefly, the procedure comprises of the following steps:
- The mother will undergo ovarian stimulation for the production of more than one mature egg (8-12 eggs) in one of her menstrual cycles.
- On the day of the egg collection, the father will provide the sperms, which will be placed in a dish along the eggs for the fertilization to occur.
- In the following 3 days, several early embryos (8-cell stage) will have developed. To test which ones are male and which ones are female, one cell from each of these embryos will be removed and sent for PGD analysis (Y-chromosome testing) in our Reprogenetics laboratory. The procedure can also be done after 5 days, at the blastocyst stage embryo, which involves removal of 5-10 cells for PGD testing.
- The PGD results are returned to us within 24 hours, and based on them, a female (XX) or male (XY) early embryo (depending on your choice) is transferred back in your womb.
- Following this procedure, the pregnancy will continue as normally.
Another advantage of gender selection is that all of your embryos will be screened by PGD, and if there are any other chromosomal abnormalities, they will be detected (for instance excess or lack of a chromosome, otherwise known as aneuploidy testing). This way, we make sure that you will be able to have the healthy baby girl or boy you desire.
What is the accuracy of gender selection?
Fertilization of 8 to 12 of your eggs with the sperm of your spouse will result in 4 to 6 embryos of one or the other sex. Even if this balance is slightly skewed, it will still leave us with enough embryos of both sexes for transfer of the embryo of your choice back in your womb. Using PGD for identifying the sex of the embryo is a very reliable method, and therefore, we can say that we will be able to deliver on your selection with 100%accuracy.