Carl Andrew Whant appeared to yawn as he was found guilty by a jury of raping the 19-year-old before stabbing her to death and setting her body on fire.
Miss Grender's family made an emotional plea for Whant, 27, to tell them the truth after a judge said the full facts of what happened in the early hours of February 5 2011 may never be known.
Days after murdering Miss Grender, who was the girlfriend of his best friend and cousin Ryan Mayes, the tattooed window salesman visited her grieving parents while crying crocodile tears and clutching a bunch of flowers.
Miss Grender's uncle Michael Brunnock said: "Nikitta was so young
and beautiful. Together with Ryan, they were to become very proud set of parents.
"This has been ripped from them by Carl Whant, who has never had the decency to tell us the truth.
"For Nikitta's mum and dad to see their grandchild for the first time in a mortuary was the most heartbreaking thing they have ever had to do."
Whant stabbed eight-and-a-half months pregnant Miss Grender to death at her home in Broadmead Park, Lliswerry, Newport, south Wales, after he had left a house party he had been at with her boyfriend in the
early hours of February 5 last year.
She and Mr Mayes were said to be excited at the prospect of becoming parents - and had already decided to call their daughter Kelsey
May.
After killing Miss Grender, Whant then set fire to her home - also risking the lives of a mother and baby who lived in the flat below.
He then returned to the party in Corelli Street, Newport - acting
as if nothing had happened, before spinning a web of lies to police about his whereabouts.
During the trial, he claimed the reason why his semen had been found inside Miss Grender's body was because he had been invited by his cousin into having consensual sex with her.
The false allegations piled more pain on 17-year-old Mr Mayes - who not only had to contend with losing his child and girlfriend - but having his sex life cross-examined in public following a terrible betrayal by the man he once regarded as "a father figure".
But during the trial, it came to light that Whant had denied ever
having sex with Miss Grender in 26 police interviews - and then took 10
months to change his story when forensic scientists uncovered vital DNA
evidence.
In sentencing him to life with a minimum of 35 years, judge Mr Justice Griffith Williams told Whant: "The murder of Nikitta Grender and
her unborn child - whose imminent birth had delighted her family and Ryan Mayes - left them completely devastated.
"Their sense of loss was compounded by the added knowledge that the murderer had raped her and tried to destroy her body.
"And their grief was then made all the more deep because you then made the false allegations that she had sex with you.
"You are a calculating, vain and devious individual and the explanation for these terrible crimes comes in part from your vanity.
"But for a moment when the mask slipped and you told police Nikitta was the first person you thought of when you fancied having sex.
(It is) a reason for these offences which never have been told.
"You knew she was unlikely to agree to sex so you went armed with a knife prepared to rape her.
"It's likely that she was prepared to let you in believing Ryan Mayes was with you.
"It matters not because however you gained entry you were able to
overpower her but not before she put up some resistance. The likelihood
is she was going to report you for raping her and that's why you murdered her."
Justice Williams added the father-of-three, who had claimed to never have cheated on his fiance, was also guilty of "extraordinary hypocrisy" by taking flowers to the teenager's grieving family after the murder.
Detective Chief Superintendent Geoff Ronayne, of Gwent Police said: "We are satisfied that justice has been served today with the conviction of Carl Whant for the horrific murder of Nikitta and Kelsey May.
"Whant has never admitted his guilt, given any indication as to why he committed this terrible crime or provided Nikitta's family with any answers."
David Wooler, Crown Advocate for the Crown Prosecution Service in
Wales, added: "The severity of the offences were such that I felt it important to acknowledge Kelsey-May's death with a separate charge in its own right. However, offences relating to unborn children cannot be charged as murder.
"This is an offence which prohibits wilful acts causing the death
of any child capable of being born alive - and given the advanced stage
of Nikitta Grender's pregnancy, Kelsey May certainly fit that description.
"Today's jury decision marks an end point to the legal process, but the effects on the family and friends of Nikitta Grender will continue for a very long time to come. Our thoughts are with them."
PA
