Advantages and Disadvantages of Early Teething for Babies Babies usually have no teeth from birth to 6 months old, but some babies start to get teeth at 4 months, and some babies don’t get teeth until 8 months old. Teething has a great impact on the growth, development and health of babies. Let’s learn more about whether early teething is good or bad for babies, and whether the opinions of the older generation are scientific and credible. Benefits: Teething is a necessary process for baby\’s growth and development. The benefits of teething mainly include three aspects. First of all, teething is beneficial to the baby’s diet. It can start as soon as the baby’s teeth grow.