What does it mean if a 5-week pregnancy ultrasound shows an incomplete gestational sac?

Patient's question:

No

Doctor's answer:

One is that it's still too early, the baby hasn't entered the uterine cavity yet, so the gestational sac cannot be seen inside the uterus. The other possibility is that it could be an ectopic pregnancy, which hasn't formed a mass outside the uterus, and it might also be something that can't be seen. So, it's hard to say for now.