Good sign that it's doesn't look or smell infected.
I wouldn't be at all surprised if she farrows earlier than expected.
Can you check her temperature? If she has a raised temperature or looks at all unwell I'd give her some long-acting antibiotics. If the discharge persists into next week or turns bloody or smelly I'd give her some antibiotics and ring your vet. But I might bet a small amount that she's just getting ready to farrow.
Good luck, and keep us posted