Large ovulation is between 20 and 24 weeks of pregnancy. By doing B-ultrasound, we can see if the fetus is abnormal, and then we can rule out the abnormality. Generally speaking, in the early pregnancy, when the fetus is found to be deformed by ordinary B-ultrasound, it is recommended to do color ultrasound for four-dimensional color ultrasound to show the condition more clearly. In addition, the radiation of color Doppler ultrasound is slightly stronger, so ordinary B-ultrasound examination is done in the first trimester, and color Doppler ultrasound will be recommended in the second trimester.

Theoretically, the difference is that three-dimensional color Doppler ultrasound and four-dimensional color Doppler ultrasound are actually images reconstructed by computer on the basis of two-dimensional color Doppler ultrasound. Two-dimensional is actually a plane, three-dimensional is a three-dimensional picture, four-dimensional is based on three-dimensional, and dynamic is a three-dimensional dynamic figure. The difference in practical application is that the examination time is different, although they are all one of the different methods of abnormality removal needed in different stages of fetal development, and they can dynamically and accurately observe the development of fetal body organs and bones. However, three-dimensional ultrasound can be performed at about 20 weeks of pregnancy, while four-dimensional ultrasound is usually performed at about 26 to 28 weeks, which is an indispensable auxiliary examination for the system's large-scale teratogenesis.

Routine items: fetal position, biparietal diameter, occipital frontal diameter, abdominal diameter, femur length, incus length, amniotic fluid, fetal movement, fetal heart rate, placenta position, placenta thickness, placenta classification and placenta lower edge. Nine screening items for large-scale abnormality: cerebellum, upper lip, gastric vesicle, four chambers of heart, kidneys, bladder, tibia, fibula, ulna, radius, spine and abdominal wall.

Make an appointment in advance. It is most suitable to have a large-scale abnormality examination around 24-28 weeks of pregnancy, so expectant mothers need to make an appointment at the hospital in advance to avoid missing the time. Too small or too large gestational age is not suitable for fetal abnormality detection. No need to empty stomach or hold your urine. There is no need to prepare for empty stomach and urine-holding. As long as pregnant women go to a regular hospital for examination within the examination time of four-dimensional color Doppler ultrasound, fetal malformation can be investigated.