The time of first period varies a lot. The average age is around 12 but anywhere between age 9 and 16 is normal. Outside of this age range may still be normal but it is worthwhile checking with a doctor. Periods usually start about two years after the first signs of puberty. Breasts beginning to develop and pubic hair growing are indications of puberty.

Possible causes of periods not starting include:

• a normal delay in development – this often runs in families, so if your mother or sister started her periods late, this may well be why your first period is delayed
• a hormonal imbalance
• being underweight
• doing too much exercise – this can affect girls who do lots of athletics, gymnastics or dance
• eating disorders
• severe stress
• pregnancy – it’s possible to get pregnant before you get your first period as your ovaries can start releasing eggs a few months before your periods start
• a problem with the uterus or ovaries