Deborah Norville is being replaced as co-host of NBC's "Today" show by Katie Couric, NBC announced Thursday.

NBC News President Michael Gartner said the decision was Norville's. He said she asked for a year off to spend time with her newborn son, Nicholas.In a statement released by the network, Norville said that "being a new mother away from the spotlight has allowed me to see clearly what I want to do: give my son the best possible start on life and practice good journalism. There is plenty of time for the latter, but I'll get only one chance to do the former."

Couric has been filling in for Norville since she went on maternity leave Feb. 22. The show's ratings have steadily improved in the five weeks since, and critical reaction to Couric has been positive.

Couric, 34, will join anchor Bryant Gumbel and co-anchor Joe Garagiola, news reader Faith Daniels and weatherman Willard Scott.

Couric was national correspondent for "Today" before filling in for Norville. She is married to Washington attorney Jay Monahan. The couple are expecting their first child in July.