There are several reasons for left abdominal pain in the first month of pregnancy: first, caused by physiological abdominal pain, which is mainly due to pregnancy, the development of the gestational sac causes the uterus to have pseudo-contraction phenomenon, this pseudo-contraction may lead to pain in the left side of the abdomen, and the uterus in the process of development and growth, can also pull the right uterine ligament to cause a certain degree of pain. Secondly, left abdominal pain may also be caused by some gynecological diseases, including left adnexitis, left ovarian cysts, etc., which can lead to left abdominal pain in pregnant women in the first month of pregnancy. Third, it may be due to intestinal diseases, including enteritis, intestinal spasm, intestinal flatulence, etc. It is also necessary to go to the hospital for a clear diagnosis and symptomatic treatment. Also, if the pain is properly intense, consider the presence of ureteral stones and other diseases on the left side, also need to go to the hospital for detailed examination and clear diagnosis.