This was mentioned in the Sunday Times letters page, so I went to check. Right enough, here it is:
'Periods: When a girl goes through puberty her ovaries release an egg every month. For a few days each month blood and other fluids pass out through the girl’s vagina. There can be some fluids called pre-period discharge before the period starts. Periods are also called menstruation. When a girl has her period, she wears a sanitary towel or tampon or menstrual cup to absorb the fluid.
During a period, girls can feel that it is a bit painful or uncomfortable. It is important to know that a girl can still do anything she wants when having her period. It’s also important to remember that not all girls have periods. Every girl
is different and unique!'
rshp.scot/second-level/
(Part 2, point 8)