"[The child's] life was ended before she had a chance to live any of it," Justice Robert Beech-Jones said during his sentence in the NSW Supreme Court on Friday afternoon.

"[She] is not just a passing reference."

More than six years have passed since the baby girl was found floating face down in a bathtub in a home in North Strathfield in Sydney's inner west just after midday on November 18, 2010.

The woman had called triple zero saying her baby had fallen from her bath seat and was submerged in the water.

Operators repeatedly urged her to return to the bathroom to pull the baby out of the water, but the woman said: "I can't go in there".

The 41-year-old pleaded not guilty to murder on the grounds she was suffering from a mental illness at the time, but guilty to manslaughter. The Crown accepted the plea earlier this year.

Soon after giving birth, the woman became increasingly anxious that her daughter had a genetic or developmental abnormality.

Numerous tests and experts told her the baby was healthy, but the woman continued to obsess.

She conducted thousands of internet searches relating to dwarfism, its symptoms and how the side effects could be surgically rectified.

The woman told staff at the Sydney Children's Hospital: "Every time I look at her, she looks like a dwarf ... it's affecting my bonding with her, and everyone in the family, including my husband, thinks I'm crazy."

One friend observed that the woman dressed the baby girl in a thick hoodie on a hot day to hide skin tags on her ears.

While the woman was high functioning and employed at a financial institution, she suffered a major underlying schizophrenic illness and her mental state rapidly deteriorated after she gave birth.

Justice Beech-Jones said the woman had let the child drown but he could not conclude that she had prepared or planned her actions.

"In a deluded state [she] ruminated on the possibility that she would be free of her mental torment if [the child] was gone," he said.

"The significant mental illness suffered before, during and after the offence permeates every aspect of these proceedings."

In bugged phone conversations, the woman was recorded saying that she had never bonded with the baby and wished she had never given birth.

The woman has spent a little under two years in custody since the baby died and has been in and out of prisons, psychiatric hospital and residential centres.

She was found unfit to be tried in 2014 and later sentenced to be detained in a facility with a limiting term of 20 years.

But the following year it was determined she had sufficiently recovered and her psychiatric condition was in "remission".

"The need and the time for her punishment has passed," Justice Beech-Jones said.

"I have no doubt that the consequences of [her] actions will remain with her for the rest of her life."

The woman, who had supporters in court, wept as she was sentenced. The four year bond includes a requirement that she continue to receive psychiatric treatment.