The midfielder missed Denmark's scoreless draw in a 2018 FIFA World Cup warm-up against Sweden at the weekend as he and his partner Sabrina Kvist Jensen awaited the birth of their first child.
"Christian became a father on Monday, the mother and boy are doing well. Christian has just arrived at the hotel and is training from today," media officer Jacob Wadland told reporters.
Denmark kick off their FIFA World Cup Group C campaign against Peru on June 16 before going on to face Australia and France.