At this time, we don't have a consensus on the titer that causes heart block and how that changes across different labs. Dr. Buyon's group did present this at ACR. So I would recommend HCQ and monitoring for this patient. 

As Dr. @Cuoghi Edens correctly alludes to, we do not know what to do. Some congenital heart block (CHB) experts say "no." It is time-consuming, expensive, and often causes unjustified anxiety in patients who have very little chance of having a baby with CHB (especially those with low titers). Then ...