The gestational sac and the meconium can be distinguished by their different shapes and structures, as follows: 1. shape 1. gestational sac: usually the gestational sac is mostly a round or oval structure, generally white in color, and there can be villi on the surface when you look at it carefully. The color is similar to the color of menstruation, and when observed in water, the meconium will mostly sink to the bottom of the water. Structure: The gestational sac is the initial structure of pregnancy and is a small embryo wrapped in amniotic membrane. As the gestational week increases, the gestational sac will have a developing fetal bud and a pulsating heart tube inside. The gestational sac can usually be seen on ultrasound after 35 days of pregnancy. The gestational sac includes the meconium, along with the fetus and components of the amniotic fluid. 2. meconium: The meconium is the tissue that forms after pregnancy when the interstitial lining of the endometrium proliferates. The meconium is the material basis for fertilized egg implantation and embryonic development. After pregnancy, the meconium tissue proliferates well to facilitate the normal development of the gestational sac. The meconium plays an important role in the implantation of the embryo and the delivery of the woman, but it does not contain the fetal or amniotic fluid components.