"Caring for and guiding young mothers who have had little or no family or community support has always been an important aspect of the Salvation Army's mission," Captain Walker said.
"This is an emotional time for our staff and also for past residents and of course the hundreds and hundreds of people who were born at Bethany."
Young women who go to the centre learn skills, including how to care for their baby, and also go on to continue their schooling through correspondence.
Testimonials on the centre's website include one from Caz, who said: "You meet young people who are in the same shoes as you.
"You make friends and stay friends and you're taught how to look after the baby. We all helped each other."
The Salvation Army has provided a service for pregnant young women for almost 114 years.
The Bethany Centre was built as a maternity hospital, but later established as a residential antenatal and postnatal support centre for young mothers.
Captain Walker said archives going back almost 100 years were still kept at the site and would be protected.
Discussions were currently taking place with organisations such as Child, Youth and Family and the district courts to ensure those girls now staying at the centre would be cared for once it closed.
Captain Walker estimated that "hundreds and hundreds" of young women had gone through Bethany's doors and said that in the past year, a total of 58 had been helped at the centre.
An event is being planned for the week before Bethany closes.