small for most women. In one study, premenopausal women who exhibited symptoms of iron deficiency were given endoscopies. 86% of them actually had gastrointestinal disease and were at risk of being misdiagnosed simply because they were menstruating. Heavy menstrual bleeding, occurring monthly, can result in anemia. Hormonal changes Side effects Menstrual health overview Moods and premenstrual syndrome (PMS) Cramps In most women, various physical changes are brought about by fluctuations in hormone levels during the menstrual cycle. This includes muscle contractions of the uterus (menstrual cramping) that can precede or accompany menstruation. Many women experience painful cramps, also known as dysmenorrhea, during menstruation. Among adult women, that pain is severe enough to affect daily activity in only 2%–28%. Severe symptoms that disrupt daily activities and functioning may be diagnosed as premenstrual dysphoric disorder. These symptoms can be severe enough to affect a person's performance at work, school, and in everyday activities in a small percentage of women. When severe pelvic pain and bleeding suddenly occur or worsen during a cycle, this could be due to ectopic pregnancy and spontaneous abortion. This is checked by using a pregnancy test, ideally as soon as unusual pain begins, because ectopic pregnancies can be life‑threatening. The most common treatment for menstrual cramps are non-steroidal anti-inflammatory drugs (NSAIDs). NSAIDs can be used to reduce moderate to severe pain, and all appear similar. About 1 in 5 women do not respond to NSAIDs and require alternative therapy, such as simple analgesics or heat pads. Other medications for pain management include aspirin or paracetamol and combined oral contraceptives. Although combined oral contraceptives may be used, there is insufficient evidence for the efficacy of intrauterine progestogens. One review found tentative evidence that acupuncture may be useful, at least in the short term. Another review found insufficient evidence to determine an effect. Interactions with other conditions Known interactions between the menstrual cycle and certain health conditions include: Some women with neurological conditions experience increased activity of their conditions at about the same time during each menstrual cycle. For example, drops in estrogen levels may trigger migraines, especially when the woman who has migraines is also taking the birth control pill. Many women with epilepsy have more seizures in a pattern linked to the menstrual cycle; this is called "catamenial epilepsy". Different patterns seem to exist (such as seizures coinciding with the time of menstruation, or coinciding with the time