The size of the gestational sac on the 48th day of pregnancy, with a diameter of about 2-3 cm is normal. Due to the growth and development speed of the gestational sac and the different lengths of the pregnant woman’s menstrual cycle and the measurement error of the ultrasound technician, the size of the developing gestational sac on the 48th day of pregnancy varies considerably, with the size of the fetal body ranging from about 0.85-1.33 cm. The gestational sac is a round, oval structure composed of amniotic membrane, embryo and network of blood vessels. The germ at 48 days of pregnancy has already taken its first human shape and can be detected by ultrasound examination as well as the primitive heart tube pulsation. If the pregnant woman has a long menstrual cycle and ovulates relatively late, the gestational sac at 48 days of pregnancy will be relatively small and the yolk sac and fetal heartbeat will appear later, at the latest no later than two months. The same size of the sac may be measured by different technicians, but as long as the development is normal, it is fine.