Ectopic pregnancy refers to the implantation of the gestational sac outside the uterine cavity, with common implantation sites including the fallopian tubes, ovaries, and pelvic cavity. Early ectopic pregnancy can also cause some pain, with common reasons for the pain including the following: First, the main reason is the enlargement of the uterus under the stimulation of estrogen and progesterone in the body, which pulls on the surrounding tissues and ligaments, such as the round ligament of the uterus, uterosacral ligaments, or bilateral adnexa, causing lower abdominal traction pain. This presents as a feeling of heaviness or menstrual-like sensation. This pain is a normal physiological manifestation during early pregnancy and is present in both intrauterine and ectopic pregnancies. Second, in early ectopic pregnancy, sometimes the gestational sac can cause mild irritation and pressure on local tissues, leading to mild localized pain, which is often not very noticeable.