At what age do testicles (testes) normally descend?

Normal Testicular Descent Timeline

Testicles normally descend into the scrotum between 25-30 weeks of gestational age, with spontaneous descent possible in the first six months of life but unlikely after six months of corrected age. 1

Phases of Testicular Descent

• Initial transabdominal descent occurs during the first trimester of gestation 1
• At approximately 22-25 weeks of gestational age, the testes are located at the internal ring 1
• The inguinoscrotal phase of testicular descent, which is androgen-dependent, occurs between 25-30 weeks of gestation 1, 2

Prevalence of Undescended Testes at Birth

• 1-3% in full-term male infants 1
• 15-30% in premature male infants 1
• Nearly 100% in extremely low birth weight infants (<900g) 1
• Prevalence decreases as birth weight increases, reaching approximately 3% in infants weighing 2,700-3,600g 1

Spontaneous Descent After Birth

• Spontaneous descent of testes may occur in the first six months of life 1
• In full-term infants, spontaneous descent rarely occurs after 4 months of age 3
• In premature infants, spontaneous descent may occur up to 6 months of corrected age 1, 3
• After six months (corrected for gestational age), testes that remain undescended are unlikely to descend spontaneously 1

Factors Affecting Spontaneous Descent

• Gestational age (premature infants have higher rates of spontaneous descent) 3
• Birth weight (lower birth weight correlates with higher rates of cryptorchidism) 1
• Hormonal factors (postnatal surge of LH and testosterone at 2-3 months appears to facilitate spontaneous descent) 3

Clinical Implications

• Primary care providers should palpate testes for quality and position at each recommended well-child visit 1
• Infants with undescended testes at birth who do not have spontaneous testicular descent by six months (corrected for gestational age) should be referred to an appropriate surgical specialist 1
• The rationale for referral by six months is the low probability of spontaneous descent after this age and the potential for continued damage to testes that remain in a non-scrotal location 1
• Early intervention (orchiopexy at 6-12 months) is now recommended as the neonatal gonocyte transforms into a type A spermatogonium at 3-12 months of age, a crucial step for subsequent fertility 2

Special Considerations

• Bilateral nonpalpable testes in a newborn male require immediate specialist consultation to evaluate for possible disorders of sex development 1
• Acquired cryptorchidism (ascent of previously descended testes) can occur later in childhood, with peak prevalence around 8 years of age 1