Every expectant mother usually has at least two diagnostic ultrasounds during her pregnancy. Currently, the most common ultrasound diagnostic instrument is B-ultrasound or color Doppler ultrasound. In recent years, more advanced three- and four-dimensional color Doppler ultrasound has emerged. So which is better for expectant mothers to have B-ultrasound or color ultrasound during normal prenatal check-ups? Will doing too much B-ultrasound affect the health of the fetus? Ultrasound examination can help doctors observe the development of the fetus, determine the size of the fetus and the more accurate due date of the expectant mother. Therefore, ultrasound examination is