Boleh je, mama! Mucus plug boleh keluar without blood, especially kalau cervix slowly dilating on its own, a few of my mum friends experienced the same thing, just clear or whitish discharge je, no panic needed. But since you're at 39 weeks and this is your first time, better check with your doctor or midwife just to be sure everything is progressing normally, okay? They'll want to assess you anyway to confirm labour is coming soon, so don't worry lah.