The 59-year-old real estate mogul and reality TV star Donald Trump is about to become a father for the fifth time, said his spokeswoman, Norma Foerderer, confirming media reports.

"It's great news for Donald and Melania. Donald is a family man, he loves children, and he's very excited," a friend told the newspaper. "He and Melania have talked about having a child, and now it's going to happen", the source added.

Melania Knaus, his third wife, is due to give birth in spring, according to New York Post. It would be the first child for the Slovenian-born model and commercial actress, who lived with Trump for three years before they exchanged vows in January, in a lavish ceremony at Trump's newly unveiled $US 42 million ($55 million) Versailles-inspired ballroom at his Mar-a-Lago resort in Palm Beach, Florida.

Knaus is said to have already started designing a sumptuous nursery in their multimillion-dollar penthouse at the top of New York's Trump Tower.

Donald Trump has four other 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.