"It is wonderful news, they are both very excited and looking forward to having their new baby," Morton's publicist, Karon Maskill, said Tuesday in a statement.
There were no other details.
Morton, 30, has a 7-year-old daughter, Esme, from a previous relationship.
She received Oscar nominations for her roles in "Sweet and Lowdown" and "In America." Other film credits include "Minority Report" and "The Libertine."