Can implantation bleeding last 3-4 days?

'Implantation bleed': Theoretically implantation bleeding could do any number of things, but honestly it's unusual to have 'implantation bleeding' at all: it's usually breakthrough for another reason.

Yes: And it could last even longer. About 1 in 3 women will experience spotting or bleeding in the first few weeks or months of pregnancy. Most of the time it is due to implantation.

No: If you bleed for 3-4 days in-between periods you should consider an evaluation.