Menstrual cycle

The menstrual cycle, also known as a period or that "time of the month", was an aspect of female reproduction.

Peril Bellamy once noted that she became "emotionally labile" just before her period. Lorris Hunsdon was slightly bothered by Peril talking about her menstrual cycle. (PROSE: Bernice Summerfield and the Library of Books)

The Thirteenth Doctor took Yasmin Khan to the TARDIS Hungarian bathroom to make her feel better during her "time of the month," giving her a hot water bottle, a bar of chocolate, and telling her the story of how her eleventh incarnation met Amelia Earhart. (PROSE: Chasing the Dawn)