Under normal circumstances, menstruation does not occur in the first month of pregnancy. If a woman feels that she is menstruating in the first month of pregnancy, it is mostly due to the possibility of pre-eclampsia. It is best to go to the hospital to have blood tests for HCG and progesterone levels. If the hormone levels are within the normal range, it is necessary to pay attention to proper rest, not to have excessive stress, and to maintain a stable mood. If the hormone level is slightly low and the woman does not have lower abdominal pain, progesterone or HCG medication can be given for fetal preservation treatment, and the hormone level can be rechecked again after a week of observation and can grow normally and in accordance with the change of pregnancy week. A gynecological ultrasound can be performed to further determine the gestational sac, its development in the uterine cavity and the presence of fetal buds and fetal heartbeat, ultimately assisting in the diagnosis of early pregnancy.