Reference chart of fetal size: 4 months pregnant, the size of the fetus is about 17 cm and the weight is about 200 grams. At this time, the fetus has fully developed limbs and can move freely in the amniotic fluid. Below we will learn how to maintain healthy fetal development from four aspects: diet, exercise, nutrition and medical care. Diet During pregnancy, diet plays a vital role in the development of the fetus. During pregnancy, pregnant women need to consume enough protein, carbohydrates and fats to ensure the healthy development of the fetus. At the same time, pregnant women should avoid eating foods that are too sweet, too salty, and too oily, as well as drinks containing caffeine and alcohol.