Purpose : It is essential to determine normative data of testicular size and penile length in newborn infants in order to assess the development during the fetal period. In this study, we evaluated testicular volumes using ultrasonography and also measured penile lengths in Japanese newborn infants. We also examined the associations of the development of these organs with factors including placental weight and anthropometric data. Methods : One hundred and fifteen full-term male newborn infants were recruited for this study. Testicular size was measured by ultrasonography. Results : Mean testicular volumes were 187.4 mm3 in the right testis and 185.4 mm3 in the left testis, and there was no significant difference between the right and left testicular volumes. Right and left testicular volumes showed positive and significant correlations with body lengths and weights. Testicular volumes in the right and left sides were not significantly associated with penile lengths. In 4 groups according to gestational weeks, testicular volume increased significantly with advance of gestational weeks in the left testis. Conclusion : We determined testicular volumes using ultrasonography in Japanese newborn infants. We believe that the results for newborn infants provide important information for assessment of the development of fetal testicular volume. J. Med. Invest. 69 : 256-260, August, 2022.
Keywords: newborn infants; penile length; placenta, ultrasonography; testicular volume.