During the growth of the fertilized egg, in the first two weeks it is called a gestational egg. As time gradually increases, each organ will slowly take shape, and the fetal bud will be formed in 40-50 days, and the fetal heart will be formed in 50-60 days, which means that the fetal bud and fetal heart will be formed in 6-7 weeks under normal circumstances. However, some people have irregular menstruation or late ovulation this month, the conception will also be late, and the formation of fetal heart and fetal bud will be delayed, so we can’t see whether there is yolk sac, fetal bud and fetal heart according to the time of pregnancy, we have to estimate the pregnancy week according to the size of the ultrasound single fetal sac. You can check again in a week to see if there is a yolk sac.