Her elder brother Christopher was born in 1277,[1] and by 1282, peaceful relations had been restored between Denmark and Sweden, leading to agreement that Princess Martha would marry Prince Birger, the heir to the Swedish throne.
[2] The alliance between the royal dynasties of Denmark and Sweden was further strengthened in 1288, when a marriage agreement was made in Helsingborg between Martha's brother, King Eric VI, and her future sister-in-law, Ingeborg Magnusdotter.
[2] According to the Erikskrönikan, Martha left Denmark already after her engagement was declared, and spent the rest of her childhood raised at the Swedish royal court until her wedding.
[2] The wedding celebrations are described as very elaborate, with a procession of knights, amateur theater by nobles and the king naming his brothers dukes.
She was praised when she asked for no dower other than the freedom of Magnus Algotsson, a noble arrested for involvement in an abduction of a bride in 1288.
[2] In a treaty between her brother, the King of Denmark, and the dukes the following year, her brothers-in-law guaranteed her possession of her dower, and in 1308, Martha and Birger were released.
[3] Her good mood was seen as a cruel sign of excitement that she and her spouse were to have their revenge for the Håtuna games, as she was aware of the plan to capture the dukes in the middle of the festivities.
Magnus, the eldest son of Queen Martha and heir to the throne, remained behind to lead the defense against the dukes' men but was captured and imprisoned.
On 4 September 1318, King Eric of Denmark granted Martha the manor of Hjarup in Jutland for her income.