The gestational sac usually appears only in the early stages of pregnancy and can be found at the base, anterior, posterior, upper or central part of the uterus. The shape of the gestational sac needs to be viewed according to the results of the ultrasound, which can usually be seen in the uterus after 40 days of pregnancy. For example, 3 x 2.1 x 1.3 is similar to a long shape and 3.5 x 3.4 x 2.9 is similar to a round shape. Normally the size and shape of the gestational sac depends mainly on the mother herself and is somewhat related to the tension and stretchable space of the mother’s uterus, for example when the mother’s uterus is relatively standard, most gestational sacs are round or oval and more clearly defined. Of course the time of pregnancy, the location of the fertilized egg, the size of the uterus and the nutrition of the pregnant woman during pregnancy are among the many factors that have a corresponding influence on the shape of the subsequent sac. In addition, if the gestational sac appears in the lower part of the uterus, or if it is irregularly shaped, not full, fuzzy, or has a rupture, you should be alert to avoid miscarriage. It should be noted that there is a rumor that the shape of the sac is related to the sex of the fetus, i.e. “a male fetus is more likely to be oval and a female fetus to be round”, but this is actually not true, as the shape of the sac cannot determine the sex of the fetus. Whether oval, striped or round, they are all normal phenomena and cannot distinguish between male and female.