They often reduce menstrual bleeding and painful menstruation cramps. In a normal menstrual cycle, declining levels of progesterone trigger menstruation. This includes muscle contractions of the uterus (menstrual cramping) that can precede or accompany menstruation. A menstrual taboo is any social taboo concerned with menstruation. Strassmann argued menstrual synchrony defined as menstruation overlap should be quite common. At puberty the first monthly period known as menarche marks the onset of menstruation. Cramps of smooth muscle may be due to menstruation or gastroenteritis. Breastfeeding delays the return of menstruation and fertility, a phenomenon known as lactational amenorrhea. Ovarian follicles secrete hormones that influence a woman's menstruation cycle. It may also occur due to prolonged sitting or standing and during menstruation or pregnancy. ESR is also higher in women during menstruation and pregnancy. Migraines are more likely to occur around menstruation. Its usual onset occurs around the time that menstruation begins. Women may have more hair and irregular menstruation. Episodes of jaundice may be triggered by stress such as exercise, menstruation, or not eating.