If the gallbladder is not visible at 30 weeks, it may be obscured by the body position of the fetus, so the pregnant woman can be allowed to exercise appropriately before conducting the examination; or it may be that the fetus does not have a gallbladder congenitally, so the pregnant woman needs to have regular checkups to observe whether there are other abnormalities in the fetus. If the body of the fetus obscures the gallbladder during the ultrasound examination, so that the doctor has no way to observe the gallbladder, then the pregnant woman can be allowed to exercise appropriately, such as climbing stairs, walking, etc., so that the fetus will change its position, and it is possible that the gallbladder of the fetus can be observed. If the fetus is born without a gallbladder, the ultrasound will not be able to observe the presence of the gallbladder. However, the absence of the gallbladder in the fetus does not pose a threat to the life of the fetus. Pregnant women need to undergo regular pregnancy checkups to observe whether there are other abnormalities in the fetus, and if the fetus belongs to a serious developmental abnormality, terminate the pregnancy if necessary. If during pregnancy checkups, it is found that the fetus does not have a gallbladder, you can consult your doctor to clarify the reason for the invisible gallbladder and further treatment will be carried out according to the reason.