Common Causes of Female Infertility Explained

When does difficulty conceiving warrant an evaluation?

The standard recommendation is to seek evaluation after 12 months of regular, unprotected intercourse if you are under 35, and after 6 months if you are 35 or older — because age-related fertility decline accelerates and earlier evaluation preserves more options 1Ref 1Practice Committee of the American Society for Reproductive Medicine (2021).Fertility evaluation of infertile women: a committee opinion.Comprehensive framework for evaluating female infertility including timing of referral, tests for ovarian reserve, tubal patency, and uterine assessment. Some situations call for earlier evaluation regardless of age:

• Irregular or absent periods (suggesting possible ovulation problems)
• Known history of pelvic inflammatory disease (PID), sexually transmitted infection, or prior pelvic surgery
• Endometriosis diagnosis
• Two or more miscarriages
• Any known reproductive structural abnormality

A reproductive endocrinologist or gynecologist will typically begin with bloodwork, a pelvic ultrasound, a uterine assessment, and a semen analysis of any male partner.

Ovulation disorders

Ovulation problems are among the most common identifiable causes. They include:

Polycystic ovary syndrome (PCOS) is one of the most frequent causes of anovulatory infertility 2Ref 2American College of Obstetricians and Gynecologists (2018).ACOG Practice Bulletin No. 194: Polycystic Ovary Syndrome.PCOS as one of the most common causes of anovulatory infertility, and ovulation induction as primary treatment. PCOS involves elevated androgens and typically irregular periods. Many people with PCOS ovulate unpredictably rather than not at all. It is also associated with insulin resistance, which can compound the hormonal disruption. Ovulation induction with letrozole or clomiphene is often an effective first step.

Hypothalamic amenorrhea — the brain's reproductive signaling shuts down in response to very low body weight, intense exercise, or significant emotional stress. Periods stop, and ovulation does not occur until the underlying cause is addressed.

Elevated prolactin (hyperprolactinemia) — prolactin is normally elevated during breastfeeding and suppresses ovulation. In non-breastfeeding individuals, a pituitary adenoma or certain medications can cause prolactin to rise and disrupt ovulation.

Primary ovarian insufficiency (POI) — ovarian function declines before age 40, causing irregular or absent periods and very low estrogen. This is distinct from normal age-related decline.

Fallopian tube problems

The fallopian tubes must be open for an egg to travel from the ovary toward the uterus and for sperm to reach the egg. Causes of tubal blockage or damage include:

• Prior pelvic inflammatory disease (PID) — often caused by untreated chlamydia or gonorrhea, which can scar the tube interior
• Prior ectopic pregnancy — treated ectopic pregnancies may leave scar tissue, and the affected tube may have reduced function or be surgically removed
• Endometriosis — can involve the tubes directly or create adhesions (scar tissue bands) that distort their position
• Prior pelvic surgery — appendectomy, ovarian cyst removal, or other procedures can leave adhesions affecting tubal function

Tubal patency is typically assessed with a hysterosalpingogram (HSG) — an X-ray dye study — or a saline infusion sonogram. If tubes are blocked or significantly damaged, IVF (which bypasses the tubes) is usually recommended 1Ref 1Practice Committee of the American Society for Reproductive Medicine (2021).Fertility evaluation of infertile women: a committee opinion.Comprehensive framework for evaluating female infertility including timing of referral, tests for ovarian reserve, tubal patency, and uterine assessment.

Diminished ovarian reserve

Ovarian reserve refers to the remaining quantity and quality of eggs. It is assessed through:

• Anti-Müllerian hormone (AMH) blood test — reflects the pool of remaining follicles
• Antral follicle count (AFC) — follicles visible on ultrasound at the start of a cycle
• Day 3 FSH and estradiol — elevated FSH indicates the pituitary is working harder to stimulate a declining ovarian pool

Diminished ovarian reserve can occur earlier than expected in some people due to genetics, prior ovarian surgery, smoking, or autoimmune conditions. It does not necessarily mean conception is impossible, but it does affect the response to ovarian stimulation and typically warrants expedited evaluation and treatment.

Uterine and structural factors

Even when ovulation and tube function are normal, the uterine cavity must be able to support implantation. Factors that can interfere include:

• Uterine fibroids (leiomyomas) — benign tumors; submucosal fibroids (those bulging into the uterine cavity) are most likely to affect implantation 3Ref 3American College of Obstetricians and Gynecologists (2021).Management of Symptomatic Uterine Leiomyomas: ACOG Practice Bulletin, Number 228.Submucosal fibroids as most likely fibroid type to impair implantation and fertility
• Endometrial polyps — small outgrowths of the uterine lining that may obstruct the cavity
• Uterine septum or other congenital shapes — an abnormal uterine shape present since birth
• Asherman's syndrome — intrauterine scar tissue from prior surgery (such as dilation and curettage) or infection

Endometriosis deserves special mention because it affects multiple parts of the reproductive system. Tissue similar to the uterine lining grows outside the uterus — on the ovaries, tubes, bowel, or pelvis — causing inflammation, adhesions, and sometimes ovarian cysts (endometriomas) 4Ref 4Practice Committee of the American Society for Reproductive Medicine (2012).Endometriosis and infertility: a committee opinion.Endometriosis as a cause of infertility via multiple mechanisms including inflammation, adhesions, and ovarian involvement. Even minimal endometriosis can reduce fertility through mechanisms that are not fully understood.

Unexplained infertility

After a complete evaluation, roughly 10–30% of couples have no identifiable cause found. This is termed unexplained infertility. It is frustrating to hear, but it does not mean nothing is wrong — it means current testing has not identified the specific problem. Many couples with unexplained infertility conceive with empiric treatment such as IUI with ovarian stimulation or IVF 5Ref 5Practice Committee of the American Society for Reproductive Medicine (2020).Evidence-based treatments for couples with unexplained infertility: a guideline.IUI with ovarian stimulation and IVF as evidence-based options for unexplained infertility.