Relatives of jailed parents Jan and Deborah Moorhead say they will fight to gain custody of the couple's unborn baby until the pair are freed.

The Moorheads are serving five years in prison for the manslaughter of their 6-month-old son, Caleb.

It was revealed in court only yesterday that Deborah Moorhead was nearly 6 months pregnant.

Jan Moorhead's sister Neryl said the news of the pregnancy was a bombshell and she would fight for the baby to stay in family care.

"I will stand by them, come what may. This is my brother ... He has been just such a wonderful person."

The Moorheads were convicted of manslaughter last week after refusing to provide Caleb with the necessaries of life. The infant had a B12 deficiency brought on by his mother's strict vegan diet that excluded meat, fish and dairy products.

The couple took Caleb out of Auckland's Starship hospital in March last year. Two weeks later he was dead.

In the High Court at Auckland yesterday, Justice Rhys Harrison said he was satisfied the authorities would know about Deborah Moorhead's uncompromising attitude and that her new baby would not suffer Caleb's fate.

Neryl, who wanted to be known by her maiden name of Moorhead, spoke to the Herald yesterday after feeling pressure from the publicity surrounding Caleb's death.

She said her family found out about Deborah Moorhead's pregnancy through the media. It came as a shock, but she was excited for them.

"They have carried on their normal lives. Why shouldn't they?" Neryl Moorhead, who has six children, talks daily to Deborah Moorhead's sister, Donna Murray.

She hoped she or Ms Murray could have custody of the child until the Moorheads had served their prison term.

Child, Youth and Family Services would not talk about the Moorhead case, but said that generally the agency would try to put a child at risk with its parents with a relative. If that was not possible, a network of caregivers was available.

Neryl Moorhead said she had visited her brother six times since he was locked up last week.

She had seen Deborah Moorhead once.

Both were in good spirits and were well cared for. Special food was being delivered to them and water was being boiled as part of their diet.

Although no one would say last night how Deborah Moorhead's pregnancy would be handled, some of the rules for pregnant inmates include:

* Access to 24-hour medical care before, during and after pregnancy.

* Access to female escorts for trips to hospital. * A staff member did not need to be there when they were examined or gave birth.

* An inmate can keep her baby up to the age of 6 months until proper provision is made for its care.

* The prison provides maternity clothes, a nightgown for the mother, a singlet, booties, bonnet, nappies, safety pins and a shawl or blanket.

Detective Sergeant Chris Scahill, who was in charge of the case, thought a prison term was appropriate for the couple.

But Jan Moorhead's father, Trevor, was upset at his son's sentence.

The Seventh Day Adventist Church continues to distance itself from the case, describing Caleb's death as an "avoidable tragedy".

Spokeswoman Bronwyn Mison said the church would work harder at highlighting a reasonable diet and encouraging use of medical services.

Vegan Society co-ordinator Sandra Murray was worried vegans would be marginalised after Caleb's death and wanted more nutritional information available for vegetarians and vegans.

What the judge said

Justice Rhys Harrison was scathing of Jan and Deborah Moorhead in sentencing the couple to five years' jail for the manslaughter of their infant son, Caleb.

* The Moorheads' failure to get medical treatment for the six-month-old was "inexcusable".

* "In other words he was starving to death."

* "He must have been suffering great and needless pain."

* "You condemned Caleb to prolonged misery."

* "If Caleb could have spoken for himself I have no doubt he would have asked for an end to the pain, and access to medical treatment."

* "The consequences of refusing to allow effective medical treatment were no different than if he had been subjected to prolonged physical abuse."