Crown Princess Mette-Marit has bowed out of several events during recent weeks, claiming illness, just as the royal program has been in one of its busiest phases ever.

That's left Crown Prince Haakon and his mother, Queen Sonja, handling the brunt of the royal duties as King Harald recovers from heart surgery. Princess Martha Louise recently delivered her own second child, and is thus out of official action herself.

A statement from the palace Monday afternoon reported that the so-called "crown couple" expect their second child in December. That suggests Crown Princess Mette-Marit's pregnancy is in a relatively early stage.

The statement went on to report that, "on the advice of her doctor," the crown princess "will take it easy" during the near future. "The situation isn't dramatic, but the doctor's advice may lead to changes in Crown Princess Mette-Marit's program," the palace concluded.

That program has been fairly full, given all the official events and festivities planned in accordance with the celebration of Norway's 100th anniversary as a sovereign nation this year. Centennial events are planned through the rest of the year, with the high points coming in May and June.

Mette-Marit was in her hometown of Kristiansand, on Norway's southern coast, on Monday when the announcement of her pregnancy came. She's due to officially open a children's film festival there on Tuesday.

Haakon and Mette-Marit already have a daughter, Princess Ingrid Alexandra, who was born last January and is next in line to inherit the throne after her father. Mette-Marit also has a son, Marius, from an earlier relationship before she met the crown prince.

The announcement of the pending royal birth in Oslo came on the same day that the crown couple in Denmark also announced that they were expecting a baby. Crown Prince Frederik was Crown Prince Haakon's best man, and the two royal families have traditionally close ties.