A small biparietal diameter of two weeks usually has no effect on the fetus. The two-week small biparietal diameter in late pregnancy usually does not lead to fetal malformation, and its main reason is the abnormal development of the fetal brain caused by malabsorption of nutrients, genetic factors, or the pregnant woman’s own nutritional deficiencies, or the pregnant woman’s own physical anomalies, which led to a decline in health, resulting in the small biparietal diameter of the fetus. Pregnant women should eat more food rich in protein during pregnancy, such as eggs, lean pork, soy products, milk and so on. It is also necessary to take appropriate supplements of food such as shrimp, fish, pork liver, oats, walnuts, peanuts, etc. Eat more fresh vegetables and fruits to ensure that the intake of food is nutritionally balanced and to avoid single nutrition. If the continuous examination found that the biparietal diameter of the fetus is small, the pregnant woman can carry out a comprehensive examination not only to determine the health of the fetus or not, but also to understand the physical health of the pregnant woman herself. Every pregnant woman should pay attention to do a good job of prenatal checkups during pregnancy, and actively listen to the advice of professional doctors to do a good job of comprehensive care and health care, which can effectively ensure the safety of the birth.