The size of the gestational sac changes daily with the week of pregnancy. In the first month of pregnancy, the fertilized egg has just completed its implantation and the gestational sac has only just formed, so its size is very small. During the ultrasound examination, it is sometimes difficult to see the gestational sac, which is expected to be about 0.2 cm. First of all, a woman’s gestational sac gradually increases in size with the number of days of menopause and there is no specific size of the sac to directly determine whether it is normal or not. However, in general, the size of the gestational sac is usually around 1-1.5 cm at around 42 days of menopause, and around 2-2.5 cm at around 50 days of menopause, while the fetal heart and germ are fully grown. Secondly, for women with irregular menstrual cycles, the time of menopause may not match the size of the gestational sac in the ultrasound examination, which is actually a normal situation, and pregnant women need not worry too much. The development of the gestational sac is related to the quality of sperm and eggs, mood and environment during pregnancy, so during pregnancy pregnant women should keep a happy mood, strengthen nutrition and pay attention to rest to promote the healthy development of the gestational sac; quit smoking, quit drinking alcohol and not to drink carbonated drinks to reduce the incidence of fetal malformations; in the diet to light mainly to reduce early pregnancy reactions.