What is infant sleep training? Is it safe? How do new parents know if their baby needs them, or should they let the baby cry it out? Are there attachment issues new parents should be concerned about when a baby cries for too long?

What is infant sleep training? Is it safe? How do new parents know if their baby needs them, or should they let the baby cry it out? Are there attachment issues new parents should be concerned about when a baby cries for too long?