How do sexually transmitted diseases (STDs) affect male fertility?

How STDs Affect Male Fertility

Sexually transmitted diseases may impair male fertility through inflammatory damage to the reproductive tract, but the evidence for a direct causal relationship remains weak and contradictory. 1, 2

Evidence Quality and Limitations

The relationship between STDs and male infertility is controversial, with most studies showing inconsistent results and methodological flaws. 1 A systematic review found that studies claiming positive associations often performed multiple analyses without appropriate statistical corrections and selectively reported outcomes suggesting correlation, while studies showing no association were equally limited in quality. 1

The most important clinical point: manifest inflammatory processes of the male genital tract caused by STDs—particularly Chlamydia and gonorrhea—often result in impaired sperm quality, but asymptomatic or adequately treated infections show unclear effects. 3

Specific Pathogens and Their Effects

Chlamydia trachomatis and Neisseria gonorrhoeae

• Chronic or inadequately treated gonorrhea can cause urethral strictures and epididymo-orchitis, which mechanically obstruct sperm transport. 4
• Both pathogens can be transmitted to female partners and cause pelvic inflammatory disease with tubal obstruction, indirectly affecting couple fertility. 4
• Acute urethritis alone has not been associated with male infertility. 4
• These infections must be treated promptly to prevent late sequelae affecting both partners. 4

Genital Mycoplasmas (Ureaplasma and Mycoplasma species)

• Large Asian studies suggest Ureaplasma urealyticum may impair sperm motility and DNA condensation. 3, 4
• Evidence from Caucasian populations is insufficient, and the pathophysiologic mechanisms remain unclear. 3
• The clinical significance of detecting these organisms in asymptomatic men is uncertain. 1

Viral STDs

• Human papillomavirus (HPV), herpes simplex virus (HSV), and hepatitis B virus (HBV) detected in semen may impair success rates of assisted reproductive techniques, though direct effects on natural fertility are unproven. 3
• HIV infection is associated with deteriorating semen quality as immunodeficiency progresses. 5, 4
• Serodiscordant couples require special counseling regarding transmission risks during conception attempts. 5, 4

Other Pathogens

• Trichomonas vaginalis has minimal to no influence on male fertility. 4
• Effects of herpes simplex virus types 1 and 2, Mycoplasma species, Treponema pallidum remain unclear due to limited studies. 2

Clinical Evaluation Algorithm

When evaluating infertile men, clinicians should obtain a reproductive history that includes STD exposure, perform physical examination for signs of genital tract infection (epididymal induration, urethral discharge), and order semen analysis. 6

Specific findings warranting STD consideration:

• Pyospermia (elevated white blood cells in semen) suggests infection or inflammation requiring further workup. 6
• Low semen volume (<1.4 mL) with acidic pH may indicate distal obstruction from prior infection. 6
• Bilateral epididymal induration or absence of vas deferens suggests prior infectious complications. 6

Testing recommendations:

• Routine semen cultures have not been prospectively demonstrated to benefit infertile couples, so screening for infection should be reserved for cases with pyospermia or clinical signs of active infection. 6
• Microbiological clarification is recommended in cases of male fertility disorders with suggestive history or examination findings. 3

Treatment Implications

Early and adequate treatment of STDs prevents late sequelae affecting fertility in both men and women. 4 However, the evidence does not support empiric antibiotic treatment for asymptomatic men with abnormal semen parameters in the absence of documented infection. 1

Key management principles:

• Screen and treat both partners concurrently, as female partner infection (particularly Chlamydia and gonorrhea) causes tubal factor infertility. 6, 4
• Chronic or inadequately treated infections appear more relevant to infertility than acute infections. 2
• Any STD increases HIV transmission risk, which has direct implications for fertility and requires specialized counseling. 4

Prevention Strategies

Utilize existing preventive measures including Chlamydia screening in young women and HPV vaccination for young males to reduce STD-related fertility complications. 3 The U.S. Preventive Services Task Force recommends screening all sexually active women under 25 years and those at increased risk for gonorrhea and Chlamydia. 6

Common Pitfalls

• Do not assume that detecting STD pathogens in semen of asymptomatic men requires treatment to improve fertility—the evidence for benefit is weak. 1
• Do not overlook female partner evaluation—STDs often cause more significant fertility impairment in women through tubal damage than in men through direct sperm effects. 6, 4
• Do not delay assisted reproductive technology while pursuing prolonged antimicrobial therapy in couples with documented STD exposure but no active infection, as the evidence for improved outcomes is insufficient. 1