The size of a 4-month-old fetus is still very small, similar to a pear, with a length of about 15 cm. The indicators for evaluating the size of a fetus include the biparietal diameter, abdominal circumference, head circumference, femur length, etc. The biparietal diameter of a 4-month-old fetus is about 3.2 cm, the femur length is about 2.0 cm, the head circumference is about 12 cm, and the abdominal circumference is about 10 cm. In the 4th month of pregnancy, the development of all organs of the fetus is basically completed. You can see through the ultrasound that the five senses of the fetus are gradually obvious, the neck is fully formed and can support the movement of the head, the organs have gradually developed and formed, the limbs can move, the toes and soles of the feet can be flexed, and the placenta and umbilical cord gradually appear. In addition, due to the stimulation of the nerves in the brain, the fetal face can appear to move, and the eyes, although closed, can feel the change of light. At this time, the pregnant woman’s stomach starts to gradually become larger, the lower abdomen is slightly bulging, and the enlarged uterus can be touched by hand. Some pregnant women can already feel the fetus’ activity in the mother’s uterus, and the discomfort symptoms such as pregnancy vomiting and pressure disappears gradually. Pregnant women need to take sufficient nutrition, have regular medical checkups, adjust their diet according to the results of the checkups, exercise appropriately and maintain a good state of mind and spirit to ensure the growth and development of the fetus.