Fetal growth characteristics: The four-dimensional color ultrasound image of the fetus at five months of pregnancy shows that the fetus is about 16-18 centimeters long and weighs about 250 grams. At this time, various data such as the fetus\’ head circumference, chest circumference, and abdominal circumference are gradually increasing. The fetus\’s abdomen is already filled with amniotic fluid, which provides sufficient conditions for its later growth. In addition, the fetus\’s limbs gradually become more flexible, the fingers and toes have formed, and