Generally the “dependent” coverage of your health plan does not extend to the babies of your children. It sounds like the baby is not covered right now.
The best option would be for the baby to be added to the spouse’s plan at work, if he has one. That generally needs to be done within 30 days of birth, or they’ll have to wait for the next open enrollment period.
Depending on your daughter’s situation, the baby might qualify for Medicaid for the Children’s Health Insurance Program. Check out InsureKidsNow.gov for more information.