The size of the fetal sac at 40 days is about 15mm, the fetus is still small at about 40 days of pregnancy, basically it has not developed much, at this time only the fetal bud and fetal heart can be seen, the fertilized egg is late, the fetal bud and fetal heart may not be seen at this time, it is a relatively normal situation, if you do not see the fetal bud and fetal heart at this time can not worry too much, it is recommended to go to the hospital after a period of time. It is recommended to go to the hospital again after a period of time for ultrasound examination to determine the development of the fetus. The first thing you need to do is to observe your physical symptoms and see if there is any bleeding or abdominal pain to avoid pre-miscarriage. When you are 40 days pregnant, the other organs of the fetus have not yet started to develop. As time goes by, the fetus will gradually grow, and in the first 3 months or so, various body organs will slowly start to form.