This one really needs a doctor to explain properly, especially at 38 weeks when you're so close to delivery. Every situation is different depending on which antibody and how high the levels are, so please don't wait to call your gynae or go in for a check-up so they can assess what it means for your baby right now. I know it's stressful to have questions like this so close to your due date, but you deserve proper answers from someone who knows your full medical history.
Better to check with your gynae or a GP if you’re unsure of any medication. Seek for medical professional advice.