Causes of Infertility

Key Points

• Infertility is multifactorial and may involve AFAB factors, AMAB factors, both partners, or unexplained causes.
• Clinical criteria commonly use failure to conceive after 12 months of unprotected intercourse, or after 6 months when the female partner is older than 35 years.
• Infertility definitions can also include inability to carry a pregnancy to live birth.
• Primary infertility occurs when pregnancy has never occurred; secondary infertility occurs after a prior achieved pregnancy.
• In current US data, infertility affects about 10 to 15 percent of males and about 19 percent of females.
• Common AFAB contributors include ovulatory dysfunction, endometriosis, tubal disease, uterine abnormalities, and endocrine disorders.
• Common AMAB contributors include impaired sperm production/transport, hormonal disorders, varicocele, and sexual-function disorders.
• Recurrent pregnancy loss (two or more spontaneous miscarriages) warrants specialist infertility evaluation.

Pathophysiology

Infertility reflects disruption of one or more required steps in conception: gamete production, transport, fertilization, and implantation. Diagnostic timing commonly uses no conception after 12 months of unprotected intercourse, or after 6 months when the female partner is older than 35 years. Clinical definitions may also include inability to carry a pregnancy to live birth. Primary infertility refers to no prior achieved pregnancy, and secondary infertility refers to infertility after at least one prior achieved pregnancy. Lifestyle and environmental factors, including delayed childbearing, obesity, smoking, alcohol use, psychological stress, environmental toxins, and untreated STI burden, can impair egg or sperm quality and reduce fecundity. Medication-associated contributors include chemotherapy exposure, prolonged or high-dose NSAID use, selected antipsychotics, and spironolactone; substance contributors such as marijuana and cocaine can also impair fertility pathways. Preexisting cardiometabolic and endocrine disease also contributes: chronic hypertension is associated with poorer egg quality and reduced sperm metrics, and thyroid dysfunction can disrupt ovulatory regularity.

AFAB infertility frequently involves hormonal-ovulatory disorders (oligoovulation or anovulation), endometriosis, pelvic adhesions, tubal occlusion, uterine/tubal structural abnormalities, and hyperprolactinemia. In one commonly reported multinational distribution, ovulatory disorders account for about 25 percent, endometriosis about 15 percent, pelvic adhesions about 12 percent, tubal blockage about 11 percent, other tubal/uterine abnormalities about 11 percent, and hyperprolactinemia about 7 percent of identified AFAB-factor cases. Ovulatory dysfunction is the largest AFAB infertility contributor and can be categorized as hypogonadotropic-hypogonadal, normogonadotropic-normoestrogenic, hypergonadotropic-hypoestrogenic, or hyperprolactinemic patterns. Hypergonadotropic-hypoestrogenic patterns include age-related ovarian decline and primary ovarian insufficiency (ovarian failure before age 40), with smoking linked to earlier follicular loss and premature menopause. Marked prolactin elevation (for example levels above about 100 ng/mL) raises concern for pituitary adenoma. Hydrosalpinx and other tubal lesions can impair gamete movement and increase ectopic-pregnancy risk, with common contributors including infection, inflammation, prior pelvic-abdominal surgery, adhesions, and structural tubal defects. Uterine abnormalities, endometrial inflammation/infection, and congenital uterine-shape variants may reduce sperm passage or implantation success. Fibroid location can also affect fertility (for example cavity-distorting or intramural lesions), and endometrial polyps are often managed before IVF when implantation impact is a concern. Chronic or postprocedure/postpartum endometritis can also contribute to implantation failure pathways. Sex-chromosome abnormalities can also influence fertility pathways, including ovarian-failure risk in Turner-pattern conditions.

AMAB infertility can present as azoospermia (no sperm) or oligospermia (low count) and may result from transport obstruction, endocrine dysfunction, altered spermatogenesis, varicocele, sperm antibodies, or ejaculatory/erectile disorders. In population analyses, AMAB factors are often the primary cause in about one-fifth of infertility cases and contribute as a combined factor in an additional substantial subset. Transport barriers include vas deferens or ejaculatory-duct blockage from infection, scarring, tumor compression, prior vasectomy, or congenital vas deferens absence. Retrograde ejaculation can lower sperm in ejaculated semen even when spermatogenesis is present. Erectile and ejaculatory dysfunction can also reduce conception probability, with contributors including age, diabetes, psychosocial stress, alcohol misuse, and selected antihypertensive medication effects. Common low-count reference thresholds include fewer than about 15 million sperm per mL of semen or fewer than about 39 million sperm per ejaculate. Gonadotoxins, heat exposure, chronic illness, medication effects, substance use, and exogenous testosterone supplementation can worsen sperm quality, motility, and production. Medication-linked contributors can include chemotherapy exposure, methotrexate, isotretinoin, systemic steroids, selected antibiotics (for example tetracycline), antidepressants associated with sexual dysfunction, and chronic opioid exposure linked to hypogonadism. Varicocele is common in the general AMAB population and can be associated with reduced sperm quality in a subset of patients, potentially through temperature-related spermatogenesis effects. Sperm-antibody infertility can occur after testicular trauma, genital infection, or vasectomy-reversal pathways. Genetic factors such as Klinefelter-pattern XXY aneuploidy can contribute to impaired spermatogenesis and infertility risk.

Male-factor evaluation commonly starts with semen analysis of concentration, motility, and morphology. A mildly abnormal single sample does not by itself confirm infertility and should be interpreted in broader clinical context.

Female-factor ovulatory patterns can be inferred from cycle history: predictable cycles every about 21 to 35 days generally suggest ovulation, while irregular cycles often suggest anovulation risk. Important anovulatory contributors include PCOS, diminished ovarian reserve, functional hypothalamic amenorrhea, pituitary-hypothalamic dysfunction, premature ovarian insufficiency, and menopause.

Classification

• Infertility type: Primary infertility and secondary infertility.
• AFAB factors: Ovulatory, tubal, uterine, endometriosis/adhesive, and endocrine causes.
• AFAB identified-factor distribution: Ovulatory (~25%), endometriosis (~15%), pelvic adhesions (~12%), tubal blockage (~11%), other tubal/uterine abnormalities (~11%), and hyperprolactinemia (~7%) in one multinational dataset.
• AFAB ovulatory subtypes: Hypogonadotropic-hypogonadal, normogonadotropic-normoestrogenic (often PCOS-associated), hypergonadotropic-hypoestrogenic, and hyperprolactinemic patterns.
• AMAB factors: Sperm-count/quality disorders, transport obstruction, hormonal causes, and sexual-function causes.
• Cross-cutting factors: Medication, toxins, infection, chronic disease, lifestyle, and psychosocial stress.

Nursing Assessment

NCLEX Focus

Prioritize identifying whether infertility cues point to ovulation, tubal/uterine structure, sperm production/transport, endocrine dysfunction, or modifiable lifestyle factors.

• Determine infertility type and timeline, including prior pregnancies and duration of conception attempts.
• Obtain focused menstrual/ovulatory, sexual, and reproductive history from both partners.
• Screen for endometriosis symptom clusters (cyclic pelvic pain, dyspareunia, and dysmenorrhea burden) when infertility concerns are present.
• Assess medication and substance exposure risks (including high-risk drugs and recreational substances).
• Screen for STI/PID history, prior pelvic/abdominal surgery, endocrine disorders, and chronic illness.
• Include baseline review of blood-pressure history, antihypertensive use, thyroid history, and recent thyroid-lab trends when infertility is being evaluated.
• For AMAB factors, review semen-analysis domains (count/concentration, motility, morphology) and exposures that impair spermatogenesis.
• For AFAB ovulatory workup, correlate cycle pattern with day-specific testing (for example day 21 progesterone, day 3 to 5 FSH, AMH, and antral-follicle assessment).
• Assess tubal and uterine factor risks and expected diagnostics (for example hysterosalpingogram for tubal patency and targeted uterine imaging/hysteroscopy when indicated).
• Include baseline endocrine and structural screening (for example thyroid testing, selected coagulation studies, and fibroid-focused evaluation) when recurrent loss or implantation failure is suspected.
• Evaluate psychosocial burden, stress response, and coping resources during evaluation or treatment.
• Screen for treatment-cycle stress, anxiety/depressive symptoms, and quality-of-life decline in both partners.

Nursing Interventions

• Provide targeted education on modifiable fertility factors: weight optimization, smoking/substance cessation, and toxin avoidance.
• Reinforce lifestyle factors linked to fertility reduction (heavy alcohol/tobacco/drug use, obesity, underweight status, endocrine-disrupting exposures, and excessive strenuous exercise).
• Teach ovulation-tracking strategies (for example basal-body-temperature charting, ovulation-predictor kits, and cervical-mucus pattern monitoring) and timing principles for intercourse during the fertile window, including intercourse at least every other day.
• Reinforce practical fertility-optimization habits for both partners: healthy weight, smoking/alcohol/recreational-drug cessation, moderated caffeine, hydration, antioxidant-rich nutrition, toxin avoidance, STI prevention, and scrotal-heat avoidance in AMAB patients.
• Reinforce STI prevention and early treatment to reduce tubal scarring risk.
• Support stress-reduction and mind-body coping resources during prolonged infertility workups.
• Offer or coordinate structured mind-body coping pathways (for example CBT-informed counseling, relaxation training, journaling, self-awareness, and social-support programs) during infertility treatment.
• Coordinate timely referral for specialist testing when severe male-factor, ovulatory, or structural causes are suspected.

Single-Cause Bias

Assuming infertility is caused by only one partner can delay complete evaluation and prolong time to effective treatment.

Pharmacology

Drug Class	Examples	Key Nursing Considerations
ovulation-induction-agents	Clomiphene and gonadotropin treatment contexts	Used for selected ovulatory dysfunction patterns with cycle-based monitoring.
biological-theories-and-therapies (dopamine-agonists)	Hyperprolactinemia treatment contexts	Prolactin control may restore ovulatory function in endocrine-related infertility.

Clinical Judgment Application

Clinical Scenario

A couple reports 14 months of infertility. The AFAB partner has irregular cycles and prior PID history; the AMAB partner uses anabolic steroids and reports reduced libido.

• Recognize Cues: Dual-partner risk factors suggest possible ovulatory, tubal, and male endocrine/sperm issues.
• Analyze Cues: Infertility is likely multifactorial rather than attributable to one isolated cause.
• Prioritize Hypotheses: Priority is comprehensive bilateral workup and urgent mitigation of modifiable factors.
• Generate Solutions: Initiate education, risk-reduction counseling, and coordinated reproductive-endocrinology referral.
• Take Action: Document timeline/risk profile and support follow-through for staged diagnostics.
• Evaluate Outcomes: Patients understand contributors, begin risk modification, and engage in complete evaluation.

Related Concepts

• fertility-and-conception - Infertility develops when one or more conception steps fail.
• amenorrhea - Menstrual absence patterns often signal ovulatory dysfunction in infertility workups.
• polycystic-ovary-syndrome - PCOS is a leading anovulatory infertility contributor with endocrine-metabolic overlap.
• genetics-in-reproductive-care - Genetic and chromosomal abnormalities are part of infertility assessment.
• treating-infertility - Cause-directed therapy depends on accurate etiologic classification.
• preconceptual-care - Early risk optimization can prevent some infertility contributors.
• family-health-and-cultural-factors - Family and social context can shape stress and treatment participation.

Self-Check

1. Which historical cues most strongly suggest tubal-factor infertility?
2. How do AMAB endocrine disorders alter sperm production and fertility potential?
3. Why is bilateral partner evaluation essential in infertility care planning?