menarche
Menstrual cycles begin at puberty. Women hit puberty at different times, just as men do. The average age for puberty is between 12 to 15 years old. Menstrual cycles usually begin somewhere within that range.
Menarche
Primary amenorrhea refers to not having a menstrual period at the age of puberty.
Puberty triggers all these developments. Menstruation shows that you are fertile and capable of reproduction.
No puberty is what makes you have a period. It can take up to 2 years until you are regular though.
I would say yes given that she has gone through puberty
that is puberty
menarche; 12
Normal fluctuations occur as a result of puberty, the menstrual cycle, pregnancy, and menopause.
If they've gone through puberty and started their menstrual cycle then yes, but that is unlikely.
... It is not possible to impregnate an infant girl until she has hit puberty and started her menstrual cycle.