Contact your employer to add them as your dependent through Special Enrollment
Please note: After you give birth, your baby is not automatically added to your health insurance plan. You have 30 days from the date of birth to add the baby to your plan, and this coverage will be considered to be effective for your baby on their date of birth. If your spouse has coverage through a different employer or insurance plan, you do not have to add the baby to both plans.
For more information, see this government resource: http://www.dol.gov/node/63379
How to Add My Adopted Child to My Coverage
1. Adoption is covered a Qualifying Life Event (QLE). If you adopt a child after Open Enrollment, contact your employer to add them as your dependent through Special Enrollment.