Question

why does mensuration occur

Answer 1

during puberty in females, the ova releases matured eggs to the uterus every 28 to 30 days for fertilisation. In case fertilisation occurs then it will result in pregnancy. If not then the ova along with the blood vessels of the uterus are shed off which causes bleeding. This is called menstruation.

Answer 2

It occurs due to the rise and fall of hormones.