Generally speaking, there is a gestational sac of 4.0* 1.5cm in the seventh week of pregnancy, and there should be obvious embryo and fetal heart beat. But at present, there are only a few embryonic buds, and there is no primitive heartbeat. The diameter of yolk sac is larger than 1.0cm, so the doctor will advise you not to keep this baby. If obvious embryo and fetal heart beat can be seen in the gestational sac, only the yolk sac is too large, which can be observed for a period of time. However, according to the present situation, you'd better think twice. It may be more risky to keep this child.
The yolk sac is too large and there is no fetal heart, which indicates that the embryo development is abnormal, which is caused by many factors, such as physical factors, external physical factors (such as radiation) or chemical factors (such as drugs and toxic substances).
I hope my answer is helpful to you.