A woman on trial for poisoning her daughter with urine injections and diarrhoea-inducing laxatives stands accused of deliberately making her ill.

Key points: Woman pleads not guilty to three charges of intending to injure her child

Woman pleads not guilty to three charges of intending to injure her child Doctors became suspicious about frequency of admissions of child for infections

Doctors became suspicious about frequency of admissions of child for infections Defence Barrister Rebekah Court decided against giving an opening address

The woman was investigated after medical staff at Sydney's Westmead Children's Hospital and the John Hunter Children's Hospital raised concerns about fast-growing organisms in her then nine-year-old's urine and blood.

The girl has a genetic illness and was regularly in both hospitals.

Doctors baffled by case at the time

The 49-year-old woman's District Court trial in Newcastle comes after officers from the NSW Child Abuse Squad started investigating in 2014.

The woman has pleaded not guilty to three counts of intending to injure her daughter by administering a noxious thing which endangered her life.

Child abuse squad detectives allege on three separate occasions a mixture of yeast and fungus grew in one of the tubes that made up the daughter's venous line, in a way that indicated contamination by urine.

The court has heard that medical staff had never witnessed such a scenario before.

"In summary senior doctors at the John Hunter and Westmead became concerned some of the girl's admissions were as a result of deliberate harm by the accused," Crown prosecutor Wayne Creasey said in his opening address.

"Blood taken showed a sudden unexplained increase in some of her electrolytes and a significant increase in her white blood cells.

"Those changes were consistent with the introduction into the bloodstream of urine, which may also have contained microorganisms.

Mr Creasey said it was in March 2015 and after four episodes of renal failure, that doctors at Westmead became particularly concerned.

"A number of doctors became suspicious about the frequency of admissions for infections and renal failure," he said.

The prosecutor said the microorganisms found on the tip of her venous line were also deemed "very troubling".

"Urine samples taken during this period showed bacteria and a number of organisms never been seen before by treating microbiologists," he said.

Scientists at Westmead Hospital. ( AAP )

Police called in

As concerns about the girl deepened at Westmead Children's Hospital, police were alerted and the woman was interviewed at a police station in Sydney.

Mr Creasey said the woman, who was a registered nurse, took with her a large handbag and an esky which were searched by officers.

"The accused was in possession of numerous medications and medical equipment, including a syringe containing a liquid, five used plastic syringes, two urine sample containers and a stool container," he said.

"The urine containers both contained a liquid residue, which the accused said was her daughter's urine and she also had laxatives in her belongings.

"The accused admitted handling infusion equipment to be helpful but said she didn't touch it if it was infusing antibiotics.

"She denied injecting urine into her line and said that she missed being a nurse and liked to be involved with the doctors."

Laxatives allegedly used to mimic gastro

The Crown alleges the woman also gave her daughter the laxative Senna to bring on gastroenteritis symptoms.

"In very broad terms, during an admission in January 2014, the girl presented with a number of complaints including constant diarrhoea and vomiting and a cause was unable to be identified," Mr Creasey said.

"Numerous medical tests were carried out and chronic laxative use was identified, in addition stool tests showed results consistent with stool samples diluted with water."

Mr Creasey alleged that stool samples had been tampered with prior to being handed to medical staff.

The court was told the girl went into care in April 2015 and was weaned off medication for six months and during that time did not have a single hospital admission.

Defence Barrister Rebekah Court decided against giving an opening address.

The trial will hear from at least eight medical experts and is expected to run at least two weeks.

