Pain in the left side of the abdomen can be caused by a variety of reasons, most likely pelvic inflammatory disease or adnexitis in women, and also in the case of ectopic pregnancy, which can also cause this pain. Women suffering from pelvic inflammatory disease can directly cause pain in the left side of the abdomen, mainly because women do not pay attention to genital hygiene in their daily lives, and prolonged bacterial infection causes inflammation in the pelvic area. If the inflammation is not treated repeatedly, it will cause pain in the left side of the abdomen, so you can go to the hospital and take oral anti-inflammatory drugs for treatment under the guidance of a doctor. This is a common gynecological disease in women, which can also cause pain in the left side of the abdomen and requires early and timely treatment to prevent the deterioration of the condition causing uterine lesions and aggravating the pain. After pregnancy, if the embryo is not properly implanted and ectopic pregnancy occurs, it will not only cause pain in the left side of the abdomen, but also vaginal bleeding.