It is generally recommended that teenage girls first see a gynecologist when they are 13, around the time when they get their first period. The average age for starting menstruation in the United States is 12 and a half years of age (or 12 years and 9 months, to be more precise). During this time, the female anatomy undergoes many changes, which is why it is recommended for girls to first see a gynecologist at this age.