"The baby is due in the spring," said Foerderer, adding that the child's gender is not yet known.
It would be the first child for the 35-year-old model and commercial actress, who lived with Trump for three years before they exchanged vows in January.
Melania, who has appeared in numerous print ads and graced the covers of Vogue and British GQ magazines, is Trump's third wife. He has four children from his previous marriages: Donald Jr., 27; Ivanka, 23; and Eric, 21, with first wife Ivana Trump, and Tiffany, 11, with second wife Marla Maples.
Trump and his Slovenian-born bride were married in Palm Beach, Fla. The setting for their opulent reception was Trump's $42 million Versailles-inspired ballroom at his Mar-a-Lago estate and club.
The New York Post, which first reported the news about the pregnancy, said the mother-to-be planned to spend time recuperating at Mar-a-Lago after giving birth.
Trump's NBC reality show, "The Apprentice," is now in its fourth season.