If it is a routine ultrasound examination in the maternity checkup, a delay of about 1 week basically will not cause much impact. However, some of the maternity tests require attention not to exceed the prescribed time, specifically the following: 1. Nuchal translucency test (NT test): usually performed at 11-13+6 weeks of pregnancy, the thickest part of the subcutaneous echogenic translucency layer in the fetal nuchal region is measured by ultrasound means and is used to assess whether the fetus may have Down’s syndrome. If the examination is postponed, the fluid under the fetal skin may be absorbed by the developing lymphatic system and thus no exact detection data can be obtained; 2. Down’s syndrome screening: performed in the middle of 15-22 weeks of pregnancy, if the examination is performed after 20 weeks of pregnancy, the disease detection rate will be significantly reduced, thus losing the significance of the examination; 3. 4D macroscopic screening: performed between 20-24 weeks of pregnancy, generally not exceed the latest examination time, because once the fetus is found to be abnormal, it will affect the life safety of pregnant women due to missing the suitable time for induction of labor. Therefore, because the growth and development of the fetus has its own rules and stages, the examination should be perfected within the recommended time to avoid affecting the accuracy of the examination results because of the missed time.