Gwent Police also confirmed the baby, discovered on wasteland close to Imperial Park on 29 January, was a boy.
The baby had been wrapped in a white towel with the words "St Annes" written along the edge and placed in the leather bag, police said.
The death is being treated as unexplained.
A post mortem previously showed the baby had been born at about full-term.
The force added it would be an "incredibly distressing" time for the baby's mother and it wanted to offer her "the right support".
Police have previously posted a video on social media urging the mother to get in touch.

The performer then forgot to switch his microphone off as he was sick.
Ramsey was only a few minutes from the end of his show at Aberdeen Music Hall when he felt sick.
The comedian, who was performing in the Granite City as part of a UK-wide tour, had earlier warned his audience that he was unwell.
He told fans on his twitter: "As a lot of you will already know, I had to run off stage last night in Aberdeen and projectile vomit was all over the place. It was beyond grim."
As well as stand-up, Ramsey starred as Jack Pearson in BBC Two sitcom Hebburn, set near his home town of South Shields in north east England.
Ramsey has also appeared on the BBC's Live at the Apollo and is a regular panellist on Channel 4 series Celebrity Juice.

A foreign ministry spokesman said the "ball is in Pakistan's court" and the "immediate issue" was their response.
Indian troops killed six militants during a four-day battle at the base in Punjab, close to the Pakistan border.
Foreign secretaries of the two sides are due to hold peace talks next week.
Although India has not officially announced any dates, Indian media reports say the meeting is due to take place on 14-15 January in Islamabad.
The assault on the Pathankot base started on Saturday, when a group of gunmen - wearing Indian army uniforms - entered residential quarters on the air base.
Seven Indian troops and six militants were killed in the gun battle.
Hopes for Delhi-Islamabad detente were raised in late December after Indian Prime Minister Narendra Modi  paid an unexpected visit to his counterpart Nawaz Sharif  on his way back from Afghanistan and the two sides announced plans to resume peace talks.
But the attack has come as a blow to the peace initiative.
"Pathankot terror attack has put renewed focus on cross-border terrorism," Ministry of External Affairs spokesman Vikas Swarup told a press conference in Delhi on Thursday.
"The government's policy towards Pakistan is clear and consistent. India wants friendly relations with all its neighbours including Pakistan," he said, adding that "India will not tolerate cross-border terror".
On Tuesday, Mr Modi urged an "immediate" response to the Pathankot attack after Mr Sharif telephoned him to discuss the incident.
Mr Sharif promised that Pakistan would take "prompt and decisive action against the terrorists", Indian officials said.
India's Press Information Bureau said India had provided Pakistan with "specific and actionable" information on the attack.
Earlier in the week, the United Jihad Council - a coalition of more than a dozen militant groups fighting against Indian rule in Kashmir - claimed that its "national highway squad" was behind the attack.
The council, based in Pakistan-administered Kashmir, is headed by Syed Salahuddin who also leads Hizb-ul Mujahidin, the longest surviving Kashmiri militant group.
Some Indian security officials have suggested the Pakistan-based Islamist militant group Jaish-e-Mohammed was to blame. India says the group is backed by Pakistan, but Islamabad denies this.
Police searching for the mother of a newborn baby found dead in Newport have released an image of a bag identical to the one the child was found in.
[NEXT_CONCEPT]
Stand-up comedian Chris Ramsey has apologised to his audience in Aberdeen after running off stage during his show to vomit.
[NEXT_CONCEPT]
India has said that planned talks with Pakistan would go ahead only if Islamabad took action against militants that Delhi said were behind the deadly assault on the Pathankot air base.