It is normal for girls to have their periods at the age of 12. Girls usually have their secondary sexual characteristics after the age of 8-9, when their breasts start to increase in size, their food intake increases, and they grow very fast. This is a normal process of puberty. When you first get your period, it can be very irregular, you may get it once and then not for the next 2-3 months, or you may get it every month, but this is not the majority of children. In addition to irregularity, the amount of menstruation is not like that of a normal mature woman, sometimes it is very small, and there may be clots. If there are more clots, it is advisable to go to a pediatric gynecologist or general gynecologist to see if medication is needed to regulate them.