The biparietal diameter of a fetus at 24 weeks of pregnancy is usually around 6.05cm, the length of the fetus is about 20-30cm and the weight is about 500-800g. 24 weeks of pregnancy belongs to the middle stage of pregnancy, the fetus is in the rapid growth period, the fetus’s organs have developed, one of the most important changes is that the fetus’s tiny bronchial tubes and alveoli began to develop, with the growth of pregnancy weeks, the baby’s weight will also grow rapidly, at this time, the baby mother needs to increase the corresponding nutrition. As the fetus is small and the amniotic fluid of the mother is relatively large at this stage, the ultrasound examination for malformations at this stage is more conducive to exposing the various organs of the fetus, which can facilitate the clinician to check whether there is any abnormality in the fetus. The first ultrasound examination of a pregnant woman is usually arranged in the 22-24 weeks of pregnancy, when the 4D ultrasound is performed, the image is more clear and three-dimensional, which is conducive to the detection of fetal anomalies. The above is only the reference development of the fetus at 24 weeks of pregnancy, and the specifics should be based on the doctor’s professional diagnosis and treatment.