Infertility can absolutely be genetic. Researchers estimate that nearly 50% of infertility cases involve genetic defects, though the picture is rarely as simple as a single gene causing the problem. Some genetic causes are straightforward, like a missing chunk of a chromosome that shuts down sperm production. Others are complex, involving dozens of genes that each nudge fertility slightly lower, especially when combined with environmental or lifestyle factors.
Genetic Causes of Male Infertility
Several well-understood genetic conditions directly impair male fertility. The most significant involve the Y chromosome, which carries genes essential for sperm production in regions called azoospermia factor (AZF) regions. When sections of these regions are deleted, the proteins needed for sperm development are never produced. Depending on which section is missing, a man may produce very few sperm or none at all. These deletions can be passed from father to son through assisted reproduction, meaning the infertility itself is hereditary.
Klinefelter syndrome is another major genetic cause. Men with this condition carry an extra X chromosome (47,XXY instead of the typical 46,XY). That extra chromosome causes the tissue in the testes to progressively stiffen and lose function, especially after puberty. Over time, the number of sperm-producing cells drops dramatically, and most adult men with Klinefelter syndrome have only scattered pockets of early sperm cells remaining. About 3% of men evaluated for infertility turn out to have this condition.
A less obvious genetic link involves mutations in the gene responsible for cystic fibrosis (the CFTR gene). More than half of men born without the vas deferens, the tubes that carry sperm out of the body, have CFTR mutations. These mutations cause cells in the reproductive tract to produce abnormally thick mucus during fetal development, which clogs and destroys the vas deferens before birth. Many of these men have no other symptoms of cystic fibrosis and only discover the mutation when they’re tested for infertility.
Genetic Causes of Female Infertility
Turner syndrome is the most common sex chromosome condition in women, affecting roughly 1 in 2,500 live births. Women with Turner syndrome are missing all or part of one X chromosome. This has a profound effect on their egg supply. A typical female infant is born with about two million eggs, but girls with Turner syndrome are born with far fewer. Studies of fetal ovaries show that 50 to 70% of egg cells in affected ovaries are actively dying, compared to just 3 to 7% in ovaries with a normal chromosome count. Women with a mosaic form of Turner syndrome, where some cells have two X chromosomes and others have only one, start with a larger egg supply and may go through puberty normally. But they still exhaust their eggs faster than other women and typically experience early menopause.
The integrity of the X chromosome’s long arm turns out to be critical for maintaining fertility in general. Women missing larger portions of this region tend to develop premature ovarian insufficiency at younger ages.
Mutations in the FMR1 gene, best known for causing Fragile X syndrome, also affect female fertility. About 1 in 200 women carry what’s called a “premutation” in this gene, where a specific DNA segment is repeated 55 to 200 times instead of the normal 5 to 40 times. Roughly a quarter of women with this premutation develop Fragile X-associated primary ovarian insufficiency, a condition where the ovaries stop functioning normally before age 40. This accounts for 4 to 6% of all cases of primary ovarian insufficiency.
Conditions With Strong Genetic Influence
Not every genetic contribution to infertility follows a clean, single-gene pattern. Two of the most common conditions affecting female fertility, polycystic ovary syndrome (PCOS) and endometriosis, have significant genetic components that interact with hormones, metabolism, and environment.
Twin studies estimate that 72% of the variation in PCOS risk is genetic. Researchers have identified dozens of candidate genes involved, spanning hormone production, insulin signaling, and fat metabolism. No single gene causes PCOS on its own. Instead, the condition likely results from combinations of gene variants that together push hormone levels and ovarian function out of balance. If your mother or sister has PCOS, your own risk is substantially higher, but inheritance doesn’t follow a predictable pattern the way something like cystic fibrosis does.
Endometriosis follows a similar model. Large genetic studies have identified more than a dozen regions of the genome associated with increased risk, many involving genes related to hormone metabolism. Having a close relative with endometriosis raises your risk, but the condition depends on many genetic and non-genetic factors working together.
How Environment Changes Gene Expression
Genetics and environment aren’t entirely separate forces when it comes to fertility. Environmental exposures can change how genes function without altering the DNA sequence itself, a process called epigenetics. This is especially well-documented in sperm.
Exposure to pesticides, plastics chemicals like BPA, and heavy metals like cadmium can alter the chemical tags that control which genes are turned on or off in sperm cells. These changes have been linked to reduced sperm production, lower motility, and abnormal sperm shape in animal studies. A high-fat diet has been shown to strip away some of these chemical tags in developing sperm, while a low-protein diet alters small RNA molecules that sperm carry. What makes this particularly significant is that some of these epigenetic changes appear to be passed to future generations, meaning a father’s environmental exposures could theoretically influence his children’s fertility.
This helps explain why two people with similar genetic backgrounds can have very different fertility outcomes. Your genes set the baseline, but your exposures and lifestyle can dial fertility-related genes up or down.
Genetic Testing and What It Reveals
Genetic testing is now a routine part of evaluating unexplained infertility, particularly in specific situations. Men with very low or absent sperm counts are typically tested for Y chromosome deletions and Klinefelter syndrome. Women experiencing ovarian failure before 40 may be tested for Turner syndrome mosaicism or FMR1 premutations. Couples who have experienced two or more miscarriages are often referred for chromosome analysis, since balanced chromosomal rearrangements like translocations cause 5 to 7% of recurrent pregnancy losses. In these cases, a parent’s chromosomes contain all the right genetic material but in a rearranged order, which leads to unbalanced chromosomes in embryos.
For couples who know they carry a genetic condition, preimplantation genetic testing (PGT-M) allows embryos created through IVF to be screened before transfer. This testing is available for over 130 different genetic conditions, with cystic fibrosis, Fragile X syndrome, and myotonic dystrophy being the most common reasons couples pursue it. Live birth rates per embryo transfer cycle run around 47%, comparable to standard IVF success rates.
Does Infertility Run in Families?
The short answer is that it can, but the pattern depends entirely on the cause. Y chromosome deletions pass directly from father to son (through assisted reproduction), making male infertility hereditary in a very literal sense. FMR1 premutations pass through families and can affect fertility in female carriers across generations. Chromosomal rearrangements can be carried silently by a parent who has no fertility problems, then cause miscarriages or infertility in their children.
For complex conditions like PCOS and endometriosis, the genetic risk is real but not deterministic. Having a family history increases your likelihood, but plenty of women with strong family histories never develop these conditions, and plenty without any family history do. The genetic component is more like a predisposition than a guarantee, shaped by which combination of gene variants you inherit and how they interact with your hormones, weight, diet, and exposures over your lifetime.