ESPE Abstracts

Introduction: Anogenital distance (AGD) is a useful marker of prenatal androgen exposure and a tool for assessment of differences of sex development. Normative data on AGD ranges for local references should be established as standards for comparison in clinical practice, but there is a paucity of data among newborns in Thailand.

Aim: To provide the sex-specific ranges for AGD in Thai full-term newborns.

Methods: A cross-sectional study was conducted in full-term newborns in Thailand, during 2016–2018. Newborns with ambiguous genitalia, dysmorphic features, and known maternal ingestion of androgenic medications or substances were excluded. During the AGD measurement, newborns were placed in a supine position. An assistant held both hips in flexion and pulled the knees back towards the shoulders. The caliper was positioned adjacent to the surface of the genitalia, with the digital screen turned away from the researcher. The AGD was measured to the nearest 0.1 mm, from anus to anterior base of penis (AGDAP) and to perineoscrotal junction (AGDAS) in males, and from anus to clitoris (AGDAC) and to posterior fourchette (AGDAF) in females. AGD ratio is defined as AGDAS divided by AGDAP in males and AGDAF divided by AGDAC in females.

Results: A total of 364 neonates aged zero to 72 hours were investigated, including 187 males (51.4%) and 177 females (48.1%). The mean ± SD gestational age was 38.69 ± 1.09 weeks. Anthropometrics data including birth weight, length, and head circumference were not significantly different between males and females by Student’s t-test. The mean AGDAS, AGDAP and AGD ratio in males were 25.20 ± 4.80, 52.60 ± 6.90 and 0.48 ± 0.08 mm, respectively. The mean AGDAF, AGDAC, and AGD ratio in females were 16.50 ± 3.90, 42.60 ± 6.20 and 0.39 ± 0.08 mm, respectively. There were significant differences between AGDAS and AGDAF, AGDAP and AGDAC, and AGD ratio between males and females (P< 0.001). The AGDAS, AGDAP, AGDAF, and AGDAC had a statistically significant but weak positive correlation with birth weight and length by Pearson's correlation analysis, but no correlation between the AGD ratio and birth weight or length was found in both sexes.

Conclusion: The sex-specific ranges for AGD in Thai full-term newborns were determined. The AGD ratio is a more reliable indicator of prenatal androgen exposure than other AGD parameters since it is significantly different between sexes and unrelated to anthropometrics.