Menstrual pain

  Menstrual pain It is a very common symptom and tends to be more common in the first 2 days of menstruation.
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  The most common causes of menstrual cramps are The endometrium produces a substance. Too much prostaglandins, which cause the uterine muscles to contract. Squeezing pain in the lower abdomen
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  In addition, other abnormal symptoms may occur, such as leg pain, back pain, headache, nausea, and vomiting.

thanks for the source
1. Faculty of Medicine Siriraj Hospital Mahidol University
2.Department of Thai Traditional and Alternative Medicine
3.Thammasat Medical Journal.