Biliary atresia is very difficult to diagnose in the fetal period because there are no obvious anatomical abnormalities or just some very minor changes that are difficult to diagnose by ultrasound. Generally, 4D ultrasound is done before 24 weeks of gestation, and even if there are some minor symptoms, it is difficult to show them due to various factors of the fetus and the mother. The fetal gallbladder is also a part of the biliary system. A small percentage of fetuses with biliary atresia will show a gallbladder that does not show up during the 4D ultrasound, and among these fetuses there may be fetuses with congenital biliary atresia, where the gallbladder does not show up from prenatal to postnatal time. The prognosis is poor in all cases of biliary atresia. If the gallbladder is not shown at the time of the fetal 4D ultrasound, then close follow-up review or further amniocentesis to test for digestive enzymes is required. Even then, it is difficult to diagnose biliary atresia in the fetal period. Since congenital biliary atresia is rare in clinical practice and cannot be detected in prenatal screening, ultrasound medicine has less research to elucidate fetal congenital biliary atresia.