Is the system column "ctid" legitimate for identifying rows to delete?

I have a table with hundreds of millions of rows that I need to delete data from. The existing indexes are the most efficient. I can however use the existing indexes to find the rows to delete by using the ctid values: DELETE FROM calendar_event WHERE ctid IN (SELECT ctid FROM calendar_event WHERE user_id = 5 LIMIT 100 FOR UPDATE) What are the risks of relying on the ctid in this case? My worst case scenario is deleting the wrong the row.