Blood test hCG 158 indicates pregnancy, but ultrasound cannot detect it. How is this?

Patient's question:

No

Doctor's answer:

Pregnancy is too early, as the embryo is too small, it cannot be seen. Pregnancy is usually around 40 days, when the size of the gestational sac can be observed. It is also not ruled out that it could be an ectopic pregnancy. It is recommended to undergo prenatal examinations.