In the first trimester of pregnancy, women will experience physical reactions such as cessation of menstruation, nausea and vomiting, frequent urination and urgency, and breast changes. 1. Cessation of menstruation: After a woman becomes pregnant, the corpus luteum secretes progesterone and the ovaries secrete estrogen, and the levels of estrogen and progesterone will rise markedly, and there is no drop in hormone levels, so the lining of the uterus will not produce a shedding, and naturally will not lead to the arrival of menstruation. 2. Nausea and vomiting: around 6 weeks of pregnancy, women will show symptoms such as aversion to grease, nausea and vomiting, drowsiness, dizziness and headache, and these symptoms are known as early pregnancy reaction in the clinic. However, most women will experience a gradual decrease or even disappearance of symptoms around 12 weeks. 3. Frequent urination and urgency: During pregnancy, due to the increasing size of the uterus, the pelvic pressure on the bladder can lead to frequent urination and urgency. 4. Breast changes: during pregnancy, women are affected by hormones, which will obviously find that the breasts are enlarged, veins are visible, nipples are enlarged, and nipple areola color is deepened and other phenomena. If the above symptoms occur, women can go to the hospital in time to carry out relevant examinations to clarify whether they are pregnant.