Giving Birth or Adopting

Yes.

Stateside:You have 90 days from your child's birth, adoption, or court appointment to register the child in DEERS and enroll the child or make any eligible enrollment changes.

Overseas: You must first register your child in DEERS within 120 days from your child's birth date or the date of adoption. Once you register them in DEERS, you then have 90 days to enroll in or change a TRICARE health plan.