The Steel yesterday confirmed it had signed the former Silver Ferns and Magic defender to play in the ANZ Championship next year.
De Bruin (32) and husband Quinton are expecting their first child in November.
De Bruin played most of this season for the Magic but had pulled out by the time the highly-fancied team was knocked out of the play-offs.
Her signing for the Steel follows the decision of experienced shooter Donna Wilkins to leave the franchise, claiming she had not received enough support as a first-time mother.
De Bruin said the franchise's commitment in supporting her desire to play top netball during motherhood was instrumental in her decision to sign.
"There are a lot of unknowns for me but the Steel have supported my decision to have my mum look after my baby while I'm focusing on my netball commitments," de Bruin said yesterday.
"That support will be very important."
De Bruin (32), who has 33 caps for the Silver Ferns, followed countrywoman Irene van Dyk from South Africa to New Zealand nearly a decade ago.
She already knows about the South, having played for the Southern Sting, as Leana du Plooy, in 2001.
She later played for the Capital Shakers, the Waikato-Bay of Plenty Magic and the Northern Force in the old national league.
De Bruin played for the Mystics in the first year of the ANZ Championship, then joined the Magic this year.
She can cover both circle positions and, at 1.90m, will add valuable height, as well as extensive experience, to the Steel, which has lost formidable defender Megan Hutton to retirement.
De Bruin joins a defensive circle that features seasoned Silver Ferns goal defence Sheryl Scanlan and New Zealand Under-21 player Te Huinga Reo Selby-Rickit.
The decision to follow other high-profile players out of the Magic had been difficult, de Bruin said.
"It was a hard decision to make but new challenges are always good," she said.
De Bruin said watching the Silver Ferns in action against the World 7 last week strengthened her resolve to get back on court.
"Just watching the Silver Ferns was enough to give me itchy feet," she said.
"When you still have that passion in your heart, it would be very hard to stop that fire."
Southern Steel chief executive Julie Paterson said she was excited about the additional experience de Bruin would bring to the team.
"She will have a big impact. We will have a really tight defensive end and that extra experience will be invaluable," Paterson said.
"Leana's height will also be a real asset, particularly given the tall shooters we've seen competing in the ANZ Championship."
All franchises are required to submit their initial squads to Netball New Zealand by October 19.
The original date of October 1 has been extended to allow franchises an opportunity to assess players competing in the national championships in Invercargill from September 28 to October 3.
The Steel still has three places open on its roster.
