Hi,
It may be normal if it only happens once, or there are some additional circumstances, like you are very young and just started menstruating, or started/stopped getting birth control pills.
Irregular menstrual periods can also be caused by hormonal imbalances, you can read more about hormonal imbalances and how you can overcome them.
Can you give some more details? How often this happened, how old you are, whether you take birth control pills, etc..?
