More than one ultrasound in early pregnancy is largely safe for the embryo and usually has no effect on the fetus. Early pregnancy refers to the period between the first and twelve weeks of pregnancy. The first ultrasound during early pregnancy, usually around 50 days after menopause, is mainly used to understand the location of the embryo’s bed, to determine whether it is a normal intrauterine pregnancy or an ectopic pregnancy, and also to preliminarily calculate the gestational week. The second ultrasound in early pregnancy refers to the NT examination around 11 weeks-13 weeks of pregnancy. The NT examination, also known as posterior nuchal translucency scan, is used to measure the thickest part of the fetal nuchal translucency layer under the skin by ultrasound, and it is used to assess whether the fetus may have Down’s syndrome. Ultrasound actually refers to a type of ultrasound, a special type of high-frequency sound wave, but one that is well-directed, penetrating, and free of ionizing and electromagnetic radiation. Ultrasounds used in medicine are low intensity and safe both for human tissue and for the fetus.