Fetal gallbladder enlargement may be caused by physiological reasons, congenital reasons, congenital malformation of the biliary tract and other factors. 1. Physiological reasons: after pregnancy, the fetus may have reduced nutritional absorption, and the gallbladder is relatively in a state of rest, which can easily cause bile stasis, resulting in an enlarged gallbladder, and it is not caused by obvious lesions of the gallbladder. 2. Congenital causes: the fetus may be born with a large gallbladder due to the influence of genetic factors or gene mutation. 3. Congenital malformations of the biliary tract: the presence of congenital malformations of the biliary tract in the fetus, such as congenital biliary atresia and congenital dilatation of the bile ducts, will lead to obstruction of bile discharge and cause the gallbladder to be oversized. Fetuses with simple enlarged gallbladder need to be dynamically observed on a case-by-case basis, or further examination is needed to confirm the diagnosis, and the prognosis is good in the vast majority of cases.