The average six-week gestational sac is around 14-16mm, but there will be individual differences. Women with regular menstrual cycle, after confirming pregnancy through early pregnancy test or blood pregnancy test, ultrasonography should be performed around 6 weeks after menopause to confirm intrauterine pregnancy and understand the development of embryo, at this time, the size of the gestational sac between 14-16mm is normal, and the fetal buds and fetal heart can also be seen, but there may be individual differences. Early pregnancy can be based on the ultrasound suggests the size of the gestational sac or fetal buds and the size of the head and buttock length to check the gestational week, and can predict the expected date of delivery. For pregnant women with a long menstrual cycle, due to the delay in ovulation and fertilization, there may be no fetal buds or fetal heartbeat during ultrasound examination at 6 weeks after menopause, so it is better to follow the doctor’s instructions to observe the situation temporarily and repeat the ultrasound examination in 7-10 days.