Anogenital distance in human male and female newborns: a descriptive, cross-sectional study.
BACKGROUND
In animal studies of the effects of hormonally active agents, measurement of anogenital distance (AGD) is now routine, and serves as a bioassay of fetal androgen action. Although measurement of AGD in humans has been discussed in the literature, to our knowledge it has been measured formally in only two descriptive studies of females. Because AGD has been an easy-to-measure, sensitive outcome in animals studies, we developed and implemented an anthropometric protocol for measurement of AGD in human males as well as females.


METHODS
We first evaluated the reliability of the AGD measures in 20 subjects. Then measurements were taken on an additional 87 newborns (42 females, 45 males). All subjects were from Morelos, Mexico.


RESULTS
The reliability (Pearson r) of the AGD measure was, for females 0.50, and for males, 0.64. The between-subject variation in AGD, however, was much greater than the variation due to measurement error. The AGD measure was about two-fold greater in males (mean, 22 mm) than in females (mean, 11 mm), and there was little overlap in the distributions for males and females.


CONCLUSIONS
The sexual dimorphism of AGD in humans comprises prima facie evidence that this outcome may respond to in utero exposure to hormonally active agents.
Salazar-Martinez
Eduardo
E
National Institute of Public Health, Av. Universidad 655, Col. Santa Ma. Ahuacatitlan, 62508 Cuernavaca, Morelos, Mexico. esalazar@correo.insp.mx
Romano-Riquer
Patricia
P
Yanez-Marquez
Edith
E
Longnecker
Matthew P
MP
Hernandez-Avila
Mauricio
M
D001003:Anal Canal / Q000033:anatomy & histology*; D000704:Analysis of Variance; D000886:Anthropometry / Q000379:methods*; D003430:Cross-Sectional Studies; D005260:Female; D005836:Genitalia, Female / Q000033:anatomy & histology*; D005837:Genitalia, Male / Q000033:anatomy & histology*; D006801:Humans; D007231:Infant, Newborn / Q000502:physiology*; D016014:Linear Models; D008297:Male; D008800:Mexico; D015203:Reproducibility of Results; D012733:Sex Differentiation / Q000502:physiology; D014566:Urogenital System / Q000033:anatomy & histology*