When you are pregnant with your baby, we recommend that you have 3 to 4 fetal ultrasound examinations. 1. 11-14 weeks ultrasound in early pregnancy: mainly for gestational age assessment and NT measurement. 2. 18-26 weeks of gestation ultrasound: mainly for systematic screening of fetal structural malformations. 3. Ultrasound examination at 32-34 weeks of gestation: mainly for further screening of fetal structural malformations. 4. Ultrasound examination before birth to prepare for smooth delivery.