Measurement for Mean Stretched Penile Length of Full-Term Newborns in Thailand
Boriboon Wangkeo¹, Weerayut Wiriyabanditkul¹
Affiliation : ¹ Division of Urology, Department of Surgery, Phramongkutklao Hospital, Bangkok, Thailand
Background: Neonatal micropenis is an essential indicator of hypogonadism. It is described as a penis that is normally formed but shorter than 2.5 standard deviations (SD) from the mean length of the penis when stretched. In contrast, the normal penile lengths of neonates have been investigated in numerous Western and Middle Eastern populations but have been barely studied in the Thai population.
Objective: To define the norms for penile length and testicular volume in Thai newborn males and to investigate the characteristic of micropenis in the Thai population.
Materials and Methods: The stretched penile length (SPL) and testicular volume of Thai male newborns were measured using an unmarked wooden spatula and a Prader orchidometer, respectively. Measurements were performed in the nursery ward within the first three days of life. Ethical approval was obtained from the Institutional Research Ethics Committee (approval No. IRBRTA 0613/2022).
Results: The study included 239 Thai male newborns, 221 of whom were full-term neonates, and 18 were pre-term. The pre-term group was excluded. The mean SPL of full-term newborns was 3.41 cm, with SD of 0.44 cm. The mean testicular volume was 2.4 mL, with SD of 0.7 mL.
Conclusion: Using 2.5 SD below the mean SPL, micropenis is defined as a SPL of less than 2.31 cm in Thai neonate. In such instances, additional investigation with more study sample is required.
Received 29 November 2024 | Revised 29 July 2025 | Accepted 18 August 2025
DOI: 10.35755/jmedassocthai.2025.10.771-775-01940
Keywords : Micropenis; Penile length; Pediatrics urology; Urologic endocrinology
