Gender selection is the process of choosing the biological sex of a child before or during pregnancy. It ranges from high-tech laboratory procedures performed alongside IVF to simpler sperm-based techniques with lower reliability. The most accurate method, preimplantation genetic testing, identifies sex with essentially 100% accuracy by analyzing embryo chromosomes before transfer to the uterus.
People pursue gender selection for two broad reasons: to avoid passing on a sex-linked genetic disease, or to choose a preferred sex for personal or family-balancing reasons. Both the technology and the ethics differ depending on which category applies.
How Embryo Testing Works
The most reliable form of gender selection happens during an IVF cycle using preimplantation genetic testing for aneuploidy, commonly called PGT-A. After eggs are fertilized in the lab, embryos grow for five to seven days until they reach a stage called a blastocyst. At that point, an embryologist removes a small cluster of cells from the outer layer of the embryo (the part that will become the placenta, not the baby itself) and sends them to a genetics lab for chromosomal analysis.
That analysis checks all 23 pairs of chromosomes, flagging embryos with missing or extra chromosomes that would lead to failed implantation, miscarriage, or genetic conditions like Down syndrome. Because the test reads every chromosome, it also reveals whether the embryo carries XX (female) or XY (male) chromosomes. Results typically come back one to two weeks after the biopsy. You then choose which healthy embryo to transfer, and that choice can include sex.
Among patients who carried a pregnancy to term after PGT-A, the success rate for having a child of the desired sex was 100% in published clinical data. The test identifies sex with near-perfect reliability because it reads actual chromosomal information rather than estimating it.
Sperm Sorting: A Less Precise Alternative
Sperm sorting separates X-bearing sperm (which produce girls) from Y-bearing sperm (which produce boys) before fertilization. The most studied version, called MicroSort, uses a laser-based technique called flow cytometry that detects the slight size difference between X and Y chromosomes. Sorted sperm can then be used for insemination or IVF.
The accuracy is meaningfully lower than embryo testing. In clinical trials, sorting for girls produced samples that were about 88% X-bearing sperm, while sorting for boys yielded about 73% Y-bearing sperm. That means the odds shift heavily in your favor, but it is not a guarantee.
An older technique called the albumin method layers sperm samples over a protein solution and collects fractions at timed intervals, based on the idea that heavier X-bearing sperm swim differently. Early claims suggested 75% accuracy for girls and 85% for boys. However, when researchers tested this method in couples actually undergoing IVF with genetic testing, the proportion of male and female embryos did not change. Independent analysis using chromosome-specific staining also failed to confirm that the sorting worked as described. Most fertility specialists consider this method unreliable.
Medical Reasons for Choosing Sex
More than 100 known genetic disorders are linked to the X chromosome. Because males have only one X chromosome (paired with a Y), a single defective copy of an X-linked gene causes disease in boys, while girls with the same mutation on one X typically have a healthy backup copy on their other X. Hemophilia, Duchenne muscular dystrophy, and certain forms of intellectual disability follow this pattern. For carrier parents, selecting a female embryo can effectively eliminate the chance of having an affected child.
A smaller group of X-linked conditions are lethal to male embryos before birth. Rett syndrome and incontinentia pigmenti fall into this category. In these cases, affected male pregnancies end in miscarriage, and only female carriers survive to birth. Gender selection can spare families repeated pregnancy losses.
When sex selection is done for medical reasons, it is broadly accepted by medical organizations and permitted by law in virtually every country that regulates assisted reproduction.
Choosing Sex for Non-Medical Reasons
The more contentious use of gender selection is elective: parents who already have children of one sex and want to “balance” their family, or who simply have a preference. This is where ethical debate intensifies and laws diverge sharply.
The American Society for Reproductive Medicine’s ethics committee holds that non-medical sex selection should not be encouraged, but that fertility doctors are not ethically obligated to either provide or refuse it. The committee identifies reproductive autonomy as the strongest argument in favor. The strongest arguments against include the misuse of medical resources for non-medical purposes, potential harm to women undergoing unnecessary IVF procedures, and the risk of reinforcing sex-based discrimination at a societal level.
In practice, many U.S. fertility clinics offer elective sex selection as part of an IVF cycle. A significant number of patients who undergo PGT-A for chromosome screening also factor sex into their embryo transfer decision.
Where It Is Legal
The legal landscape splits into three categories. Most countries with IVF regulations prohibit sex selection except for medical reasons. The United Kingdom, Canada, Australia, Germany, Belgium, the Netherlands, New Zealand, and Poland all fall into this group. Each allows an exception when the goal is to avoid a serious sex-linked genetic condition, but elective selection is explicitly banned.
Spain classifies non-therapeutic sex selection as a “very serious infraction” under its reproductive law. Switzerland permits sex selection only in limited medical contexts.
The United States has no federal law addressing sex selection at all, which means clinics can offer it freely. Mexico and Japan similarly lack specific regulations covering the practice. France’s IVF law does not mention sex selection. This regulatory silence effectively makes elective gender selection available in these countries, though individual clinics set their own policies.
Risks of the Procedure
Gender selection through PGT-A carries the same risks as any IVF cycle: hormonal stimulation side effects, egg retrieval discomfort, and the emotional and financial weight of the process. The biopsy itself adds a specific concern. Removing cells from a developing embryo is an invasive step, and the effect on the embryo’s potential is not trivial.
Research using time-lapse imaging has shown that embryos biopsied at the early cleavage stage (day three) develop more slowly afterward, compacting later than normal and hatching from their outer shell in an atypical pattern. These embryos tend to be smaller with a thicker outer shell. Older biopsy techniques that remove cells at the cleavage stage can deplete up to 25% of the embryo’s cell mass, which may reduce implantation rates.
Current practice has shifted toward biopsy at the blastocyst stage (day five through seven), which samples only cells destined to become placental tissue rather than the embryo itself. This approach is considered safer, though no large, well-controlled studies have definitively quantified its long-term developmental impact. Children born after PGT-A biopsy have not shown increased rates of birth defects in the data available so far, but the technique is relatively young and long-term follow-up studies are still maturing.
What the Process Looks Like in Practice
If you pursue gender selection through IVF with PGT-A, the timeline typically spans six to eight weeks from the start of ovarian stimulation to receiving your genetic results. You begin with hormone injections to stimulate egg production, followed by an egg retrieval procedure. Eggs are fertilized in the lab, and embryos grow for five to seven days. Those that reach the blastocyst stage and meet quality thresholds are biopsied, then frozen while the cells are sent for analysis.
Results arrive in one to two weeks and tell you two things about each embryo: whether its chromosomes are normal, and whether it is XX or XY. If you have multiple healthy embryos of your preferred sex, you select one for a frozen embryo transfer in a subsequent cycle. If none of your embryos are both chromosomally normal and the sex you want, you face the decision of transferring a healthy embryo of the other sex, discarding embryos, or starting another IVF cycle.
Cost varies widely by clinic and region but generally falls between $15,000 and $25,000 in the United States when you factor in the IVF cycle, genetic testing fees, and frozen embryo transfer. Insurance rarely covers elective sex selection, though some plans cover parts of the IVF cycle if there is also a medical indication like infertility.