The newlyweds live in a small back- section flat owned by Mrs Bain since 2007, in the Christchurch suburb of Redwood. Mr Bain, 42, works at a local engineering firm.
His wife goes by her family name of "Miss Davies" at Cotswold School in the Christchurch suburb of Bishopdale where she is a Year 6 teacher and Maori and Pasifika leader. She is still teaching and not yet showing, a family friend said yesterday.
"They had plans from the start to have kids," the source said.
"They have told their close friends but just want to play things very quiet."
Mr Bain was convicted in 1995 of murdering his Dunedin family and spent 13 years in jail before he was acquitted in a 2009 retrial.
Long-time Bain supporter Joe Karam said he was "absolutely delighted" for the couple.
"I think they will be great parents and I hope they have a lovely family life," he said.
The former All Black said the "very special occasion" would be even sweeter if Justice Minister Judith Collins "had respected the will of the nation and honoured the report commissioned by her government in settling David's compensation claim".
Mr Karam was referring to the three polls conducted in February and March last year which showed a two-to-one majority in favour of Mr Bain receiving compensation.
A report by former Canadian Justice Ian Binnie found that on the balance of probabilities, Mr Bain was innocent of murdering his parents, two sisters and brother in Dunedin in 1994 and had been wrongfully imprisoned.
Last year Mr Bain's lawyer, Michael Reed QC, announced he was seeking a judicial review of how Ms Collins handled the Binnie report.
In February 2013 Cabinet agreed to a request from Mr Bain to put the compensation bid on hold until the judicial review had been heard.
Last month Ms Collins' office told the Otago Daily Times the substantive hearing could be held later this year.
Mrs Bain's mother, Carolyn, is a long-time Bain supporter, having visited him in prison and billeting him during his second trial in the High Court at Christchurch. When the couple's engagement was made public, she said she was "delighted" to welcome him to the family.
David Bain's life
1994 - David Bain's parents, two sisters and brother are shot and killed in their Dunedin home.
1995 - Jury finds Bain guilty of murdering his family. He is sentenced to a mandatory life term.
1995 - Court of Appeal dismisses appeal.
2007 - Five-day Privy Council hearing in London begins. It orders a retrial.
2009 - Bain is found not guilty on five counts of murder, following a retrial.
2010 - Bain asks the Government for compensation for 13 years in prison.
2012 - Justice Minister Judith Collins rejects Justice Binnie's report after Robert Fisher, QC found a number of alleged errors.
January 10, 2014 - Bain marries Liz Davies in a private ceremony at a Christchurch vineyard.
June 2014 - The couple announce they are expecting their first child.