Answer:
minimum 30 days after the child is born, and up to 60 days if you purchased your plan through a health exchange
Step-by-step explanation:
The Health Insurance Portability and Accountability Act (HIPAA) of 1996 established that newborns (or newly adopted children) will be automatically eligible for coverage with the same insurance provider as his/her mother. The insurance company must provide a minimum 30 day window to the parents in order for them to enroll the newborn into the family's health plan.
For plans not acquired through a health exchange, the mandatory coverage extension ends at midnight day 30, day 31 is not covered.