What term describes a menstrual period that is regular but prolonged with heavy flow?

Menorrhagia is the term used to describe a menstrual period that is both regular and prolonged, characterized by heavy menstrual flow. It specifically refers to excessive bleeding during menstruation, often defined as losing more than 80 mL of blood during a menstrual cycle or having menstrual bleeding lasting longer than seven days.

This condition can be attributed to various causes, including hormonal imbalances, uterine fibroids, adenomyosis, or other underlying health issues. The regularity of the menstrual cycle, combined with the increase in duration and flow, distinguishes menorrhagia from other menstrual irregularities.

The other options refer to different menstrual disorders: oligomenorrhea involves infrequent menstrual periods, metrorrhagia refers to irregular bleeding between periods, and hypomenorrhea indicates unusually light menstrual flow. Therefore, menorrhagia accurately describes the scenario presented in the question, making it the correct choice.