It is possible that a girl’s small biparietal diameter is related to her relatively small skull. The degree of development of each child is different, if it is not particularly small, will not affect the normal development, then do not need to worry too much; if it is less than the normal range, need to do further examination to see if it is anencephaly or craniosynostosis and other conditions, to determine the cause of the disease before taking treatment measures. If you are just a little malnourished, you should eat more protein and vitamin-rich food, and pay attention to the meat and vegetables in your diet, don’t be partial, and make sure that the fetus has a sufficient supply of nutrients.