Oligomenorrhoea is the term used to describe irregular periods and those lasting over 35 days.

The most common causes are related to menstrual cycles where no egg is produced (anovulatory cycles). This can occur leading up to the menopause (climacteric) and in women with polycystic ovaries. When no cause is found, this and other menstrual symptoms form part of the condition known as dysfunctional uterine bleeding.