I Got Pregnant With His Majesty's Child -A Biography of Queen Berta-

Berta is wed to the king as his second wife in a loveless, political marriage. However, after Berta falls pregnant with his child, the royal palace is thrown into disarray. The king's first wife stews in jealousy and a deep-seated sense of betrayal as Berta and King Harold's relationship begins to change.

(Source: MANGA UP!)