At thirty-one weeks, the fetus is about thirty-five to forty centimeters in length, twenty-five to twenty-eight centimeters in parietal length, and weighs about one thousand to one thousand seven hundred grams. The thirty-first week of pregnancy is the late stage of pregnancy, when the fetus grows and develops faster, the length of the fetus is about 35 to 40 centimeters, the length of the top hip is about 25 to 28 centimeters, and the weight is about 1,000 to 1,700 grams. There are variations from pregnancy to pregnancy and this is not absolute. In the thirty-first week of pregnancy, you can estimate your weight by ultrasound examination, combining the biparietal and vertex-hip diameters and abdominal circumference, and consult a doctor if any abnormality is detected. After pregnancy, you should do regular maternity checkups to detect any problems in time and deal with them promptly.