Their babies were the first to be born in New Zealand to a haemophilia carrier using pre-implantation genetic diagnosis (PGD).
Only a few babies have been born worldwide using this technology.
It allowed checks to be made of the couple's embryos when they were at the eight-cell stage to see if they were either carriers of haemophilia or affected by the disease.
Mrs Najafi is a carrier of haemophilia, something she could have handed down to a son.
She was worried about having a baby with haemophilia, having observed its debilitating impact on her late father and knowing that it had affected nine other family members.
Before the technology was refined, embryo selection to prevent haemophilia meant all male embryos were discarded because there was no way of telling if they had the disease.
Similarly, there was no way of knowing if female babies were carriers.
The birth of daughter Rania and son Arian was the culmination of about five years of perseverance for the couple, a difficult time which included failed in vitro fertilisations and miscarriage and some time out of work for Mr Najafi after he was made redundant.
When the Otago Daily Times caught up with the couple recently, the twins were lively and contented, although more than a little suspicious about having their photographs taken.
Their parents described Rania as quite serious and sensitive and quick to cry, while Arian was loud, loved rough and tumble and noise.
While the couple are enjoying parenthood, a sadness for the family has been the recent unexpected death of Mr Najafi's mother back in Iran.
The family is hopeful they may be able to visit the remaining family in Teheran - Mr Najafi's father, his two older brothers and an older sister, a niece and nephew as well as a great-nephew.
He is the only son to have children carrying on the family name.
Another hope the parents have for the new year is a few more hours' sleep as the babies are still waking at least once a night, and sometimes more frequently.
Mr Najafi said the babies were generally in a routine and as long as they were able to keep that routine, life was "almost stress free".
His wife laughed at that sentiment but agreed that keeping the twins' daily sleep routine was important.
They agreed that life was easier now than it was when the babies were smaller but also realised that once the pair began crawling and walking their lives would get busier.
Following the earlier article about the babies, which mentioned the couple had been unable to afford a double buggy, a reader donated a buggy no longer being used, a gesture for which the couple are most grateful.
