Anogenital distance in healthy Infants:Method-, age- and sex-related reference ranges.

CONTEXT The use of anogenital distance (AGD) in clinical and epidemiological settings is increasing; however, sex-specific reference data on AGD and data on longitudinal changes in AGD in children is scarce. OBJECTIVE To create age-, sex- and method-related reference ranges of AGD in healthy boys and girls aged 0-24 months, to assess the age-related changes in AGD, and to evaluate the two predominantly used methods of AGD measurement. DESIGN The International AGD consortium (IAC) comprising four centers compiled data from one cross-sectional and three longitudinal cohort studies (clinicaltrials.gov (NCT02497209). SETTING All data were collected from population-based studies, recruiting from four maternity or obstetric centers (The USA, Cambridge, Odense, and Copenhagen). SUBJECTS This study included a total of 3,705 healthy, mainly Caucasian children aged 0-24 months on whom 7,295 measurements were recorded. MAIN OUTCOME MEASURE(S) AGDAS (ano-scrotal), AGDAF (ano-fourchette), AGDAP (ano-penile), AGDAC (ano-clitoral), AGD-body size indices (weight, BMI, BSA, and length), and intra- and interobserver biases. RESULTS We created age-specific reference ranges by centers. We found that AGD increased from birth to 6 months of age and thereafter reached a plateau. Changes in AGD/BMI during the first year of life were minor (0-6% and 0-11% in boys and girls, respectively). CONCLUSIONS Reference ranges for AGD can be used in future epidemiological research and may be utilized clinically to evaluate prenatal androgen action in DSD patients. The increase in AGD during the first year of life was age-related, while AGD/BMI was fairly stable. The TIDES and Cambridge methods were equally reproducible.