What happens when a girl starts her period?

First period: Menarche usually occurs between ages 11 & 13 in the us. However for some their period could start as early as age 9 & for others not until 16. Before you have a period, you will have noticed breast development, pubic hair & white to yellowish vaginal discharge. Before the first period a girl may feel bloated, develop cramps in legs or abdomen & feel moody (depressed or anxious).