Vision and Dental Insurance for Baby
As a general rule of thumb a child pediatrician will check babies eyes at their regular doctor visits. Which is generally covered under your major medical (however you should refer to your own policy terms and conditions to confirm that). Vision insurance may be needed for a child if advise by your baby pediatrician (say if glasses are needed)
For dental a child should have dental insurance before their first birthday. The ADA advises that a child should see a dentist at the time they cut their first tooth, but no later then their first birthday. Dental care starts even before teeth come in so having insurance will help with the cost of seeing a dentist.