Sex-specific ranges and ratios for anogenital distance among Thai full-term newborns
Nattakarn Numsriskulrat, Khomsak Srilanchakon, Chaiyat Pronprechatham, Sopon Pornkunwilai, Vichit Supornsilchai
Abstract
Abstract Introduction Anogenital distance (AGD) is a marker of prenatal androgen exposure and a tool for assessment of differences of sex development. Data for AGD in newborns have been published, but these findings may not be applicable to Thai newborns. Aim To provide the sex-specific ranges for AGD in Thai full-term newborns. Methods A cross-sectional study was conducted in term newborns in Thailand, during 2016–2018. AGD was measured from anus to anterior base of penis (AGD AP ) and to perineoscrotal junction (AGD AS ) in males and from anus to clitoris (AGD AC ) and to posterior fourchette (AGD AF ) in females. AGD ratio is defined as AGD AS divided by AGD AP in males and AGD AF divided by AGD AC in females. Results A total of 364 newborns were studied (male 51.4%). The mean AGD AS , AGD AP and AGD ratio in males were 25.20 ± 4.80, 52.60 ± 6.90 and 0.48 ± 0.08 mm, respectively. The mean AGD AF , AGD AC , 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 AGD AS and AGD AF , AGD AP and AGD AC , and AGD ratio between males and females ( p < 0.001). The AGD AS , AGD AP , AGD AF , AGD AC were correlated with birth weight and length, but AGD ratio showed no correlation. Conclusion The sex-specific ranges for AGD in Thai full-term newborns were determined. AGD ratio is a useful marker of prenatal androgen exposure since it differs between sexes, but constant between races and did not vary by body size.