In an e-mail to friends and supporters, Sandlin and her husband, former East Texas Rep. Max Sandlin, said they are looking forward to a "particularly blessed holiday."

Spokesman Russ Levsen said the pregnancy will not affect Herseth Sandlin's re-election this year. He said the late December due date works well with the congressional schedule, since Congress is not expected to be in session at that time.

The Sandlins, both Democrats, were married in March 2007. Max Sandlin has four children from a previous marriage.