The normal value of the biparietal diameter of a fetus at 17 weeks of pregnancy is about 3.7cm, which may fluctuate slightly depending on the growth and development of each fetus. The biparietal diameter of the fetus reflects the level of growth and development. At 17 weeks of pregnancy, the fetus is already in the middle stage of pregnancy, which is a period of more rapid development of the fetus’s skeleton, and the biparietal diameter will change significantly, and the normal value of the biparietal diameter at this time is about 3.7cm. The normal value of biparietal diameter at this time is about 3.7cm. If the nutritional intake of the pregnant woman is high, it may increase slightly, if the nutrition of the pregnant woman is insufficient, the biparietal diameter of the fetus may decrease. It is recommended that pregnant women carry out timely pregnancy checkups to observe the development of the child’s biparietal diameter, and if there are abnormalities, they need to consult a doctor in time to determine whether there are chromosomal abnormalities in the child, and take appropriate methods of intervention.