1. Changes in belly size at 18 weeks of pregnancy. At 18 weeks of pregnancy, the fetus has grown to about 13 centimeters long and weighs about 150 grams. At this time, the mother\’s belly has begun to bulge significantly, but it is still not obvious. This is because the baby is still very small and is gradually enlarging. 2. How should pregnant women stay healthy? During pregnancy, women need to pay more attention to their diet and physical condition. First of all, ensure adequate daily intake of nutrients, such as protein, carbohydrates, fats, vitamins and minerals. Secondly, we should pay attention to avoid bad habits such as smoking and drinking, and have regular childbirth