The normal position of the anus is not defined objectively. Using a simple technique, the anal position index was designed to define the position of anus in neonates and infants as follows: the ratio of the distance between the scrotum and the anus to the distance between the scrotum and the coccyx for males and the distance between the vagina and the anus to the distance between the vagina and the coccyx for females. The anal position index in neonates was not affected by body weight. In male infants, the anal position index was not affected by age. But in female infants, the anal position index decreased from neonatal period to three months of age but no significant difference was demonstrated from three months of age to twelve months of age. We think that the anal position index is useful as an objective parameter to assess the localization of the anus.
