Do you have any scriptural evidence that anyone was ever aborted from the new Birth or Scriptural evidence of someone having to be born again, again?
Of course.
Christ said that not all who call on His name will be saved. When asked what one is to do in order to be saved, His response was to follow His commandments and then give away all posessions and follow Him. Another time Christ commanded to participate in the Eucharist which is His flesh and blood. Many disciples left Him at that point. In one parable Christ compares the Kingdom of Heaven to seeds scattered in good and bad soil; some seeds don't make it. In another He compares a Christian life to the unending work of a servant who is not entitled to rest even after he had served a full day in the field. In short, as St. Paul said, we are to "work out our salvation with fear and trembling"; neither baptism, or, even less so, one-time conversion experience is not a guarantee of salvation.
I alluded to several scriptures that you are probably familiar with and will supply verse references if it becomes necessary.