The hare lip, also known as cleft lip, is a relatively common facial deformity in daily life, often discovered during pregnancy by doing ultrasound. If ultrasound reveals that there is a break in the continuity of the lips, the presence of hare lip should be considered. The causes of hare lip include the following aspects: First, the most common reason is because the gestational sac in the process of growth and development during the early pregnancy, the structure of the fusion of the problem, resulting in the interruption of the local structure. Secondly, in some cases, hare lip is a comprehensive manifestation of multiple chromosomal malformations in the whole body. For example, some chromosomal malformations can cause multiple structural malformations, which are easily manifested as hare lip. If a woman delivers a child with a harelip, it is best to test the chromosomes so that the next pregnancy can be guided to avoid delivering another child with an abnormality.