The parents of a premature baby testified in court Thursday that she was left severely disabled after nurse Lucy Letby allegedly tried to kill her.

Letby, 32, who is on trial in the United Kingdom, is accused of murdering seven infants and attempting to murder 10 others at the Countess of Chester Hospital’s neonatal unit during a year-long killing spree between June 2015 and June 2016.

A jury at Manchester Crown Court heard evidence relating to one child, know as Baby G, whom Letby allegedly tied to kill on three separate occasions.

VIDEO SHOWS ROOMS AT NEONATAL UNIT WHERE LUCY LETBY ALLEGEDLY MURDERED BABY

A court sketch shows Lucy Letby appearing at Warrington Magistrates' Court via video link, Nov. 12, 2020. The neonatal nurse is accused of murdering seven babies and the attempted murder of another 10.

A court sketch shows Lucy Letby appearing at Warrington Magistrates' Court via video link, Nov. 12, 2020. The neonatal nurse is accused of murdering seven babies and the attempted murder of another 10. (SWNS)

Prosecutors allege Letby put extra milk and air into the infant’s system, causing irreversible brain damage.

The court heard testimony that Baby G was born premature at 23 weeks at six days, weighing just 0.535 kg, or a little over one pound, at Arrowe Park Hospital before being transferred to the Countess of Chester in August 2015.

She was 100 days old — the equivalent of 38 weeks gestation — when Letby first tried to kill her which, prosecutor Nick Johnson said, made her the "youngest and smallest" of the 17 babies in the case.

The jury heard how Baby G suffered a collapse around 2 a.m. on Sept. 7, 2015, after Letby had started a night shift at the hospital.

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In statements read in court the baby’s parents — who can’t be named for legal reasons — described how they believed she was doing well up until that point.

U.K. neonatal nurse Lucy Letby and a stock image of newborn babies

U.K. neonatal nurse Lucy Letby and a stock image of newborn babies (ER Productions Limited via Getty Images/SWNS)

Her father described receiving a call from the hospital that morning to say their daughter was "vomiting" and had been aspirated but that he shouldn’t worry.

He’d traveled to the hospital with the baby’s mother, he said, and become more concerned to learn it was actually "projectile vomiting."

Baby G was stabilized, but when he saw her afterward, he realized something was wrong.

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"I knew something had changed," the father said.

"When she was in the incubator at the Countess of Chester she would smile at the sound of my voice," he said. "After the vomit, she was different, and she did not respond to my voice anymore."

He said an MRI scan later revealed the extent of her brain damage, and she now has quadriplegia cerebral palsy.

Countess of Chester Hospital on July 3, 2018, in Chester, United Kingdom.

Countess of Chester Hospital on July 3, 2018, in Chester, United Kingdom. (Anthony Devlin/Getty Images)

The child also has microcephaly, a condition where a baby’s head is smaller than normal, breathing issues, is visually impaired, requires a feeding tube and needs 24-hour care.

Earlier, the jury was told how concerns were raised among medical staff after Baby G started projectile vomiting and struggled to breathe, and her abdomen appeared "distended and discolored."

The baby was intubated and transferred to a different room, according to medical notes, but she remained unwell for several hours.

A doctor who was called to the neonatal unit also noted the baby’s "large projectile vomit" and "purple and distended" abdomen, with "blood-stained fluid" from the trachea.

A police officer stands outside Lucy Letby's house, July 4, 2018.

A police officer stands outside Lucy Letby's house, July 4, 2018. (Christopher Furlong/Getty Images)

After finishing her shift, Letby exchanged text messages with a colleague in which she described the baby’s collapse as "awful" and then asked, "Any idea what caused it?"

Baby G was returned to Arrowe Park Hospital in the early hours of Sept. 8, and by the next week, she was well enough to be transferred back to Countess of Chester.

ALLEGED KILLER NEONATAL NURSE LUCY LETBY WROTE CONFESSION NOTE: 'I AM EVIL. I DID THIS.'

It’s alleged Letby then made two further attempts to murder Baby G on the same day — just five hours apart — on Sept. 21.

Prosecutor Johnson previously told the jury that she suffered the "same problem" she had on Sept. 7, but this time it followed a documented feed by Letby.

He said, "There had been no significant issues with G at all. She had vomited because she had been given excessive milk and air."

The jury was shown video of a room at the hospital’s neonatal unit where Letby allegedly murdered a newborn baby before attempting to murder his twin brother.

The jury was shown video of a room at the hospital’s neonatal unit where Letby allegedly murdered a newborn baby before attempting to murder his twin brother. (UK Crown Prosecution Service.)

It hadn’t happened "by accident," he added, and there were parallels with other babies targeted by Letby.

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It’s alleged she was the "common denominator" and the baby’s deaths coincided with her shifts.

Letby, from Hereford, England, denies all 22 charges against her and the trial is expected to last six months.