Four-dimensional ultrasound mainly through the measurement of fetal femur length roughly determine fetal height, but affected by many factors, and can not accurately determine fetal height. Four-dimensional ultrasound is based on three-dimensional ultrasound plus the time dimension as a parameter, can observe the real-time dynamic activity image of the fetus, four-dimensional ultrasound best time is between 26-29 weeks of pregnancy. It mainly examines the development of the fetal face, nervous system, spine, urinary system and digestive function, and should intervene in time if abnormal fetal development is found. Factors affecting fetal height development mainly include genetic factors, environmental factors and maternal nutritional factors. Pregnant women should pay attention to the prenatal examination during pregnancy, actively listen to the advice of professional doctors to do a comprehensive nursing care, pay attention to rest, at the same time should relax, avoid tension, anxiety, any discomfort should be timely to the hospital, by the doctor to clarify the diagnosis, and cooperate with the doctor to deal with the symptoms.