Gender Selection refers to any process that increases the probability of having a child of a desired sex. Family Balancing is gender selection when the purpose is to select for the gender that is underrepresented in the family. For example, if a family has two boys and one girl then they would qualify for family balancing to have another girl.
Family balancing requires one or both of two techniques. MicroSort® is an experiment technique, awaiting FDA approval, in which the sperm are sorted into those containing an X chromosome (leads to GIRLS) or a Y chromosome (leads to a BOY). PGD (preimplantation genetic diagnosis) is the technique of removing a cell from an embryo formed with IVF to determine the genetic sex of the embryo. Then the embryos of the desired sex are transferred into the uterus. Please read the section for each technique for details.
If you REQUIRE a nearly 100% probability of the desired sex then PGD must be used. PGD alone will provide a nearly 100% probability of the desired sex.
MicroSort® increases the probability that the perm that inseminates the egg will have the chromosome that leads to the desired sex. MicroSort® can be important even when we use PGD, because we want the high quality embryos to be of the desired sex. The MicroSort® web site indicates that the sort purity is 88% for X-chromosome sorts and 74% for Y-chromosome sorts. The the MicroSort web site and the blog page for additional details.
If you are content with an 88% chance of a girl with an X-sort or 74% chance of a boy with a Y-sort, then PGD is unnecessary.
MicroSort® frozen-thawed sperm usually fertilizes eggs normally in IVF when used with ICSI (intracytoplasmic sperm injection).
About 75% of eggs will fertilize normally and only 33% of embryos will be high quality. So, if MicroSort® increases the likelihood of the embryos from 50% to 74% (Y-sort) and 88% (X-sort), then we should expect many more high quality embryos of the desired sex.