Two Sydney parents who neglected their baby by feeding her a vegan diet have escaped a jail term despite the girl suffering long-term medical issues.

Key points: The mother and father both cried as the judge delivered her findings

The mother and father both cried as the judge delivered her findings They will serve 18 months of an intensive corrections order in the community

They will serve 18 months of an intensive corrections order in the community The baby fell far behind development milestones and her bones did not develop after birth

The 35-year-old man and 33-year-old woman were charged last year after their daughter had a seizure and was admitted to Sydney Children's Hospital in March.

For the first 19 months of her life she was fed a "conservative vegan diet" and became malnourished, suffered rickets and missed key developmental milestones.

The couple, who cannot be named for legal reasons, pleaded guilty in December to failing to provide for a child, causing danger or serious injury.

The mother and father both wept and hung their heads in the dock as District Court Judge Sarah Huggett described the girl's medical problems.

The child after eight months in foster care. ( Supplied )

While Judge Huggett said she was not passing moral judgment on those who choose plant based foods, she said the girl's diet was "completely inadequate" for her to thrive.

"It is the responsibility of every parent to ensure the diet they choose to provide to their children ... is one that is balanced and contains sufficient essential nutrients for optimal growth," she said.

"This child was severely malnourished, underweight and undersized, and delayed as far as age-appropriate milestones were concerned.

"There must have been ample opportunity for her condition to be acted upon."

She sentenced each offender to 18 months of an intensive corrections order in the community and 300 hours of community service.

The maximum sentence for the offence was five years in jail.

Two sultanas for a snack

Hospital tests revealed the baby had multiple severe nutritional deficiencies and Osteopenia, or thin bones.

Medical staff said her bones had not developed since birth.

The girl's diet consisted of oats with olive oil, rice milk, vegetables, rice, potatoes and tofu, and her snacks consisted of a mouthful of fruit or two sultanas.

A foster carer who first met the girl when she was aged 19 months was shocked to see how far behind her growth milestones she had fallen.

Through a victim impact statement, she told the court the girl looked like a three-month-old baby, weighing only 4.89 kilograms and had no teeth.

While the carer said the girl became more interactive with play and cuddles, her height and weight remained disproportionate.

"When she meets new people they ask her questions about her age and are shocked," she said.

"They will often stare at her and ask questions. She stands out as different."

The judge said he took into account the mother's depression. ( Supplied )

Psychiatrist Dr Yvonne Skinner did not believe the mother was suffering postnatal depression so severe as to affect her ability to care for the girl.

However, that was contradicted by Dr Stephen Allnutt who believed she showed other symptoms consistent with major depression, including ambiguity towards decision-making and a loss of motivation.

Judge Huggett accepted the woman was suffering from depression and this reduced her moral culpability to some extent.

The girl has since been reunited with her two older siblings and is in the care of a paternal aunt in Queensland.

Both offenders have supervised access to the children.