Ovulatory problems are the single most common identifiable cause of female infertility. Together with unexplained infertility they account for more than 50% of all infertility etiologies (Best Practice & Research Clinical Obstetrics & Gynaecology 2015).
Male factor is present in 40–50% of couples, which is why a couple’s evaluation should never start with the woman alone (ACOG Committee Opinion 781).
The ProIVF Medical Editorial Team assembled this guide from ACOG guidance and WHO-commissioned epidemiology, plus PubMed-indexed systematic reviews. Registry data comes from ASRM, SART and the CDC assisted-reproductive-technology program. Every figure below was checked against the primary abstract, and the medical advisory board reviews each guide before publication.
When Is It Actually Infertility?
Infertility is a defined clinical threshold, not a feeling of failure. ACOG defines it as failure to conceive after 12 months of unprotected intercourse in women under 35, or after 6 months in women 35 and older.
“Infertility, defined as failure to achieve pregnancy within 12 months of unprotected intercourse or therapeutic donor insemination in women younger than 35 years or within 6 months in women older than 35 years, affects up to 15% of couples.” — ACOG Committee Opinion No. 781, 2019
Women over 40 warrant immediate evaluation rather than a waiting period, and the same opinion puts unexplained infertility at up to 30% of couples (ACOG CO 781).
How Common Is It Really?
Two numbers answer this, and they rest on different denominators. Primary infertility — never having conceived — affected 1.9% of women aged 20–44 exposed to pregnancy risk in 2010 (Mascarenhas et al., PLOS Medicine 2012).
Secondary infertility is measured only among women who already have a live birth, and 10.5% of them could not conceive again. In absolute terms, affected couples rose from 42.0 million in 1990 to 48.5 million in 2010.
What Happens If Nothing Is Treated?
Timing matters more than most people expect: about 80% of conceptions occur within the first six cycles in which intercourse falls in the fertile phase. After 12 unsuccessful cycles, roughly 55% of untreated subfertile couples still have a live birth within the next 36 months, and about 5% are definitively infertile by 48 months (Human Reproduction 2005).
That is the argument for evaluating early but not panicking: most couples do conceive, and the small group who will not is identifiable.
What Causes Infertility in Women?
Causes are not equally common, and most couples have more than one contributing factor.
| Cause group | What the data show | How it is confirmed |
|---|---|---|
| Ovulatory disorders | Ovulatory defects plus unexplained causes together exceed 50% of all etiologies | Cycle history, mid-luteal progesterone, ultrasound |
| PCOS | Global prevalence 7.9%–12.1% by diagnostic criteria (general female population); 46% of female-factor cases in a 120-couple clinic series | Rotterdam criteria: ultrasound + androgens + cycles |
| Tubal factor | 20% tubal and 16% adhesions among women with unexplained infertility at laparoscopy | HSG / HyCoSy, laparoscopy |
| Endometriosis | 5% (2–9%) of the general population; 38% (25–51%) among women with infertility | Laparoscopy (definitive), MRI for deep disease |
| Adenomyosis | 1% (0–2%) general population; 31% (10–58%) in infertility populations | Ultrasound / MRI |
| Age-related / ovarian reserve | Cumulative live birth after 6 retrieval cycles (optimistic estimate): 86% under 35 vs 42% at 40+ | AMH, antral follicle count |
| Male factor | 40–50% of couples | Semen analysis |
| Unexplained | 15–30% after standard work-up | Diagnosis of exclusion |
Are Ovulatory Disorders Really the Biggest Single Cause?
Yes among identifiable female causes: ovulatory defects plus unexplained causes exceed 50% of all etiologies (Best Pract Res Clin Obstet Gynaecol 2015).
Polycystic ovary syndrome sits at the front of that group. Its pooled global prevalence is 12.1% (95% CI 9.8–14.8) using Rotterdam criteria, and 7.9% (6.2–9.9) under stricter definitions (Human Reproduction Update 2026) — a general-population rate, not a share of clinic patients.
The clinic picture is narrower. In a series of 120 couples at a public facility in Mumbai, PCOS was the leading female-factor cause at 46% of female-factor infertility (J Hum Reprod Sci 2019). Thyroid dysfunction, high prolactin and hypothalamic amenorrhea complete the list; details are in the PCOS and fertility guide.
What Does Tubal Factor Infertility Mean?
Damaged or blocked fallopian tubes stop egg and sperm meeting, and the damage is usually silent. Among women investigated for unexplained infertility, laparoscopy found tubal factors in 20% and adhesions in 16% (Reproductive Biomedicine Online 2024).
Pelvic abnormalities were far more likely in women who had already received fertility treatment: 75%, versus 53% in those who had not.
Infection is the dominant driver: in the same 120-couple Mumbai series, pelvic inflammatory disease and tuberculosis were significantly associated with tubal factor infertility (p = 0.001). The pathway from diagnosis to IVF is covered in the tubal factor guide.
How Much Does Endometriosis Really Contribute?
Endometriosis is far more common in infertility clinics than in the general population. Pooled prevalence is 5% (95% CI 2–9%) overall, but 38% (25–51%) among women presenting with infertility (Reproductive Biology and Endocrinology 2025).
Adenomyosis — endometrial-like tissue growing into the uterine muscle — follows the same pattern in the same review: 1% versus 31%.
Among women whose standard work-up found nothing, 44% have endometriosis at laparoscopy, most of it minimal or mild (74%) (RBM 2024). Surgical and IVF decisions are laid out in the endometriosis and IVF guide.
Do Fibroids and Polyps Block Pregnancy?
Only some, and location decides: submucous fibroids and cavity-distorting fibroids matter, while intramural and subserous ones often do not; polyps and intrauterine adhesions disturb implantation directly. Which ultrasound finding must be treated before a transfer and which can wait is compared in gynecological conditions and fertility.
How Much Is Age, and How Much Is Ovarian Reserve?
Age acts through both egg number and egg quality, and IVF does not cancel it. In a single-center analysis of 6,164 patients and 14,248 cycles, cumulative live birth after six retrievals was 86% under 35 but 42% at 40 and over (Malizia et al., NEJM 2009).
Both figures are optimistic estimates: they assume women who dropped out would have succeeded at the rate of those who stayed. The conservative counterparts are 65% under 35 and 23% at 40 and over. The authors’ own conclusion: “IVF may largely overcome infertility in younger women, but it does not reverse the age-dependent decline in fertility.”
Low AMH and its interpretation are handled in the low AMH guide, and per-age success data in IVF success rate by age.
What If Every Test Is Normal?
That is the unexplained category — 15–30% of couples after a standard work-up — and it is not a neutral label. In one IVF cohort, 742 women (48%) carried an unexplained-infertility diagnosis, and the label fell more often on women aged 35 or older (52% versus 40% under 35).
Age changes what the label means. Among women under 35, live birth was actually higher with unexplained infertility (47% versus 38%); among older women it fell to 27% versus 34% (Human Reproduction 2024).
The adjusted odds ratio for live birth in older women with unexplained infertility was 0.63 (0.43–0.94) — a further 37% reduction in IVF effectiveness for the group with the least time to absorb it.
Which Test Answers Which Question?
A complete work-up answers six separate questions, and skipping one is the usual reason diagnosis is delayed.
- Are you ovulating? Cycle history plus a mid-luteal progesterone (a blood test timed about a week before the period); PCOS and thyroid or prolactin causes need further bloodwork and ultrasound.
- Are the tubes open? HSG (an X-ray dye test) or HyCoSy (its ultrasound equivalent) as first line, laparoscopy when endometriosis or adhesions are suspected.
- Is the cavity normal? Transvaginal ultrasound with saline sonography (sterile fluid instilled to open the cavity) for polyps, submucous fibroids and adhesions.
- How many eggs remain? AMH (a blood marker of remaining egg supply) plus an antral follicle count (a vaginal ultrasound count of small resting follicles), interpreted by age rather than as a standalone verdict.
- Is the partner’s semen normal? Semen analysis — the cheapest test in the whole work-up, and the one most often postponed. See the semen analysis guide.
- Are there symptoms pointing at endometriosis? Cyclical pelvic pain and deep pain during intercourse justify imaging or laparoscopy even when the tubes look normal.
Symptoms that justify skipping the waiting period entirely are listed in signs of infertility.
How Does Each Cause Change the Treatment Path?
The diagnosis determines whether treatment is worth trying at all.
- Ovulatory disorders respond to oral ovulation induction, often with IUI (intrauterine insemination), and are the group where weight and metabolic treatment change outcomes.
- Tubal factor does not respond to medication: with blocked tubes or a hydrosalpinx (a fluid-filled blocked tube), IVF is the route. Most centers drain or remove a hydrosalpinx before transfer, because that fluid lowers implantation.
- Endometriosis surgery can improve natural chances in mild disease, but suppressive drugs do not improve fertility, so time spent on hormonal suppression is time not spent trying.
- Cavity problems — polyps, submucous fibroids, adhesions — are corrected hysteroscopically, usually before any transfer.
- Age-related decline and low reserve shift the priority to speed: fewer diagnostic detours, and donor eggs become the realistic route at advanced maternal age (donor egg IVF).
- Unexplained infertility is treated empirically with IUI or IVF, and the age interaction above should be part of that conversation.
- Male factor moves the couple to ICSI (a single sperm injected into each egg) regardless of the female diagnosis (ICSI guide).
Can Any of It Be Prevented?
Partly, and the levers are less glamorous than supplement marketing suggests.
- Infection: chlamydia and gonococcal infection are the leading preventable cause of tubal damage, so prompt testing and treatment of partners matters more than any fertility diet.
- Weight: overweight and obesity exceed 50% prevalence in some developed countries and interact directly with ovulatory infertility (Best Pract Res 2015).
- Smoking and alcohol: both accelerate ovarian aging, and neither has a safe level when conception is planned.
- Timing: the age curve is steeper than most people assume — see IVF success rate by age for the numbers by band.
- Elective procedures: curettage and uterine surgery carry adhesion risk, which is why cavity assessment follows repeated procedures.
Three Women, Three Diagnoses
The same complaint arrived through three different mechanisms, and each pathway had its own price.
Shared with consent; names and identifying details changed. Amounts reflect the published ranges cited in this article.
Lin, 33, accountant, Hangzhou. Irregular cycles since adolescence, no pain, normal AMH. PCOS confirmed on ultrasound and androgen panels; letrozole (an oral ovulation-induction drug) plus timed intercourse at a public hospital, with monitoring and medication costing about US$600 across three cycles. Pregnant in cycle four with a healthy boy in 2025. “I had been told to lose weight for ten years. Nobody had said ovulation induction existed,” she said.
Yuan, 36, nurse, Chengdu. Two years of trying after one early miscarriage, normal hormones, a blocked left tube and a hydrosalpinx on the right after an untreated infection in her twenties. Laparoscopic salpingectomy followed by IVF in Bangkok: US$11,400 for the combined surgical and treatment package, inside the US$6,000–12,000 range Thai clinics publish. One boy born in 2024. “My AMH was fine. The problem was plumbing, and no blood test would have shown that,” she recalled.
Mei, 41, entrepreneur, Shenzhen. Four years of unexplained infertility, all tests normal, three failed IUIs. She moved to IVF in Los Angeles with her own eggs. Two retrievals cost US$26,500, at the upper end of the US$15,000–30,000 range, and a single euploid (chromosomally normal) transfer gave one live birth. “The label ‘unexplained’ felt reassuring until I read that it predicts worse IVF results after 35. That is what made me stop waiting,” she said.
FAQ
Q: What is the most common cause of infertility in women?
Ovulatory disorders lead the identifiable causes, and ovulatory plus unexplained causes together exceed 50% of etiologies. PCOS on its own affects 12.1% of adult women worldwide under Rotterdam criteria — a general-population figure, not its share of infertility patients.
Q: Can you be infertile with regular periods?
Yes. Regular cycles make an ovulatory cause less likely, but they say nothing about the tubes, the uterine cavity, endometriosis or sperm.
Laparoscopy finds tubal damage in 20% of women whose work-up was labeled unexplained.
Q: How many couples have no cause found?
15–30% after a standard work-up, and ACOG puts unexplained infertility at up to 30% of couples. It is a diagnosis of exclusion, and its IVF prognosis depends on age.
Q: Does endometriosis always cause infertility?
No. Pooled prevalence is 5% (2–9%) in the general population versus 38% (25–51%) in infertility clinics, so most women with endometriosis conceive — but the odds are clearly shifted.
Q: Which test should be done first?
Semen analysis: it is the cheapest test in the pathway, male factor is present in 40–50% of couples, and finding it first removes years of unnecessary female investigation.
Q: Is low AMH the same as infertility?
No. AMH predicts how ovaries respond to stimulation far better than it predicts natural conception, and low reserve still leaves pregnancy possible.
Age is what moves the outcome: cumulative live birth after six retrievals falls from 86% under 35 to 42% at 40+, even on the optimistic calculation.
The practical consequence is urgency and protocol choice, not a verdict. See the low AMH guide.
Q: At what age should I stop trying naturally?
Evaluation, not stopping: ACOG advises assessment after 12 months under 35, after 6 months at 35 and older, and immediately over 40. Cumulative live birth after six retrieval cycles drops from 86% under 35 to 42% at 40+, even on the optimistic estimate, so time is the variable you can still control.
How to Plan Your Next Step
Four moves that shorten the path to a diagnosis:
- Count the cycles, not the years — 80% of conceptions happen within six cycles, so a defined start date makes the 12-month (or 6-month) threshold usable.
- Test the partner in parallel — male factor is involved in 40–50% of couples, and semen analysis costs a fraction of any imaging.
- Ask which finding explains which symptom — a normal hormone panel does not exclude tubal disease, and a normal AMH does not exclude endometriosis.
- Match the treatment to the mechanism — medication for ovulation, surgery for the cavity, IVF for tubes and severe male factor.
Costs and success rates differ widely by destination. Our verified hospital directory lists published program prices alongside CDC and SART outcome data, and you can contact the ProIVF team to compare clinics for your specific diagnosis.
About this article: Researched and written by the ProIVF Medical Editorial Team from ACOG Committee Opinion No. 781, WHO-commissioned prevalence analyses, and PubMed-indexed systematic reviews and cohort studies, with AI-assisted tools used only for literature organization and initial drafting under editorial direction. Reviewed by the ProIVF Medical Advisory Board; our editorial standards are on our About page.
Last updated: October 1, 2026
