Brief Answer:
Pregnancy test can show positive for few days
Detailed Answer:
Hello and welcome to Ask A Doctor service.
I have reviewed your query and here is my advice.
Since the pregnancy kits can detect very small amounts of hcg in blood, the test can be positive for few days after the miscarriage.
It can also show positive in cases of missed abortion, incomplete abortion and rare ectopic pregnancy. That is why it is recommended to repeat the test after 3 weeks of miscarriage. If other symptoms are there like discharge from vagina or fever, then ultrasound is done to check for retained products of conception.
Hope this answers your query. Let me know if I can assist you further.
Dr Vaishalee