Ardern was elected Deputy Leader of the Labour Party on 1 March 2017, after the resignation of Annette King. Just five months later, after Labour's leader Andrew Little resignation, Ardern was elected as party leader. She led her party to win 14 seats at the 2017 general election on 23 September, winning 46 seats to the National Party's 56. After working with New Zealand First, a minority coalition government with Labour and New Zealand First was formed, supported by the Green Party. Ardern became Prime Minister and she was sworn in by the governor-general on 26 October 2017. She became the world's youngest female head of government at age 37. Ardern later became the world's second elected head of government to give birth while in office when her daughter was born in June 2018.