The slow development of fetal legs refers to the short femur length of the fetus, which may be caused by maternal malnutrition, abnormalities of the placenta or umbilical cord, and abnormalities of fetal development. 1. Maternal malnutrition: Pregnant women are prone to malnutrition due to partiality, vomiting and insufficient intake of nutrients. Maternal malnutrition can affect the development of the fetus, which can be manifested in the slow development of the fetus’s legs. 2. Abnormalities of the placenta or umbilical cord: abnormalities of the blood supply to the placenta and the umbilical cord around the neck can lead to fetal ischemia in the uterus, which can affect the growth and development of the fetus, and the slow development of the fetus’s legs can be seen. 3. Abnormal development of the fetus: structural abnormalities and endocrine abnormalities in the fetus itself can also lead to abnormal development of the fetus, which may result in slow development of the legs. In case of slow development of legs, it is necessary to go to the regular hospital for further examination in time, and actively cooperate with professional doctors for treatment and treatment.