In the second month of pregnancy, the belly will not be obviously bigger for the following reasons: First, women are in the early pregnancy period in the second month of pregnancy, most women will have nausea, vomiting and other gastrointestinal discomfort reactions, less diet, there may be no weight gain or even weight loss, the belly will not become bigger. Secondly, another situation is that due to the small development of embryo in the second trimester, the uterus enlarges in the pelvic cavity and does not grow out of the pelvis, and the belly will not appear to increase significantly. After the third trimester, the early pregnancy reaction gradually disappears, the amount of food and drink will increase, and the organs of the fetus have already developed and taken shape and are growing faster, so the uterus will grow out of the pelvic cavity and there may be a significant increase in the size of the stomach. Only in a few cases where there are multiple pregnancies, or where there is hyperemesis gravidarum, the uterus will grow out of the pelvic cavity and the belly will become bigger at two months.