Causes of Infertility in Women and Men: What the Data Shows

Infertility has many possible causes, and they often overlap. NICHD notes that problems in the male are as likely as problems in the female, that causes can come from both partners, and that in many cases the exact cause is never found.^[1] This guide summarizes the most common causes described by US health agencies and shows how often each diagnosis appears in IVF data reported to the CDC. It is general information, not a diagnosis.

Causes of female infertility

Ovulation problems

NICHD describes failure to ovulate as the most common overall cause of female infertility, occurring in 40% of women with infertility issues.^[2] Possible reasons include:^[2]

• Ovarian conditions such as polycystic ovary syndrome (PCOS) or primary ovarian insufficiency (POI)
• Aging, including diminished ovarian reserve, a low number of eggs due to normal aging
• Endocrine disorders, such as thyroid disease or problems with the hypothalamus
• Lifestyle and environmental factors

Structural problems

Blocked fallopian tubes stop eggs from reaching the uterus and sperm from reaching the egg. Problems with the uterus can interfere with implantation.^[2] NICHD lists endometriosis, uterine fibroids, polyps, scarring in the uterus and an unusually shaped uterus. It notes that most women with fibroids do not have fertility problems.^[2]

Infections

Untreated gonorrhea and chlamydia can lead to pelvic inflammatory disease, which can scar and block the fallopian tubes.^[2]

Other factors

MedlinePlus lists further possible causes, including autoimmune and clotting disorders, diabetes, eating disorders or poor nutrition, being overweight or underweight, smoking, drinking too much alcohol, chemotherapy, and older age.^[4]

Causes of male infertility

NICHD reports that men are the only cause or a contributing cause in about 40% of couples’ infertility problems.^[3] The most common issues affect how the testicles work; others involve hormone imbalances or blocked or missing ducts.^[3]

• No sperm (azoospermia): the cause in about 15% of infertile men, according to NICHD. It can result from a hormone imbalance or a blockage.^[3]
• Low sperm count (oligospermia): NICHD names varicocele, an enlarged vein in the scrotum, as the most common cause, and says varicocele is present in about 40% of men with fertility problems.^[3]
• Sperm transport problems: blockages, vasectomy, erectile dysfunction or retrograde ejaculation. NICHD says an inability to transport sperm causes about 10% to 20% of male infertility cases.^[3]
• Conditions affecting sperm formation: chromosome disorders such as Klinefelter syndrome, diabetes, high prolactin, testicular injury, undescended testicles, thyroid problems, and infections such as mumps.^[3]

MedlinePlus adds heavy use of alcohol, marijuana or cocaine, exposure to high heat for long periods, some medicines, obesity, smoking, cancer treatment and older age.^[4] See male infertility and ICSI.

Unexplained infertility

The CDC uses “unexplained infertility” when no cause is found in either the woman or the man.^[6] NICHD calls this idiopathic infertility.^[1]

How often each diagnosis appears in US IVF data

US clinics report to the CDC the reasons for each assisted reproductive technology (ART) treatment. The table shows only the infertility-related categories. More than one reason can apply, so shares overlap.^[5]

Diagnosis (CDC category)	National share, 2022	2021	2020
Male factor	28%	28%	28%
Diminished ovarian reserve	26%	27%	28%
Other reason, infertility	26%	24%	28%
Ovulatory dysfunction	14%	14%	14%
Unexplained infertility	11%	11%	10%
Tubal factor	10%	11%	11%
Recurrent pregnancy loss	7%	6%	6%
Endometriosis	6%	6%	7%
Uterine factor	6%	6%	6%

In 2022, male factor was the most frequently reported infertility diagnosis (28%), followed by diminished ovarian reserve (26%).^[5] The CDC defines diminished ovarian reserve as a reduced ability of the ovary to produce eggs.^[6]

These shares describe people who used IVF, not everyone with infertility. Many people with ovulation problems, for example, are treated with medication and never need IVF.^[1] The data also includes non-infertility reasons such as egg or embryo banking, which are not shown in this table; see what is infertility? for the full list.

Why the cause matters for treatment

The likely cause shapes which treatments are considered. The WHO notes that some causes of infertility are preventable.^[7] NICHD says fertility medications are most likely to benefit women whose infertility is due to ovulation problems, and least likely to help when the fallopian tubes are damaged or endometriosis is severe, although IVF can help in those cases.^[8] For men, medication can treat some hormone problems, surgery can repair some blockages, and ART can be effective if surgery does not restore fertility.^[9] See IUI vs. IVF and fertility testing: what to expect.

Questions to ask a clinician

• What tests are needed for both partners, and what will each one tell us?
• Is there a likely cause, or is our infertility currently unexplained?
• Which treatment options make sense for this cause, and in what order?
• How does age affect the options and timing in our case?

Find a clinic

Clinics vary in the services they offer. Browse US fertility clinics by state, compare reported outcomes, and see our questions to ask a fertility clinic.