A very large stomach in the second trimester is usually not normal and may be due to multiple pregnancies, hyperemesis gravidarum, uterine fibroids and so on. During pregnancy, as the fetus grows and develops, the uterus will gradually increase in size, resulting in a noticeable bulge in the stomach. However, in the second month of pregnancy, the stomach is usually not obviously protruding because the pregnancy is too short and the uterus is still in the pelvis. At this time, the belly is not normal, but can not be ruled out is caused by obesity. 1. Multiple pregnancies: If it is twins or multiple births, the position of the uterus may be more than the pelvis in the second month of pregnancy, resulting in a noticeable increase in the stomach, which is a normal situation. 2. Gestation: Generally, the size of uterus in gravidas is obviously larger than the uterus of normal pregnancy in the corresponding month, and the patient will have obvious symptoms such as nausea and vomiting, abdominal pain, irregular vaginal bleeding, etc., and the symptoms of pregnancy are more serious, which can be diagnosed clearly by ultrasound and blood HCG test between normal pregnancy and gravidas. 3. Uterine fibroids: If a woman has uterine fibroids before pregnancy, uterine fibroids will also grow rapidly after pregnancy, especially within 4 months of pregnancy. During pregnancy, you should take regular pregnancy checkups, observe the growth and development of the fetus, and go to the hospital in time if you have any discomforts, so that the doctor can make a clear diagnosis and cooperate with the doctor to deal with the symptoms.