Lucy Letby has formally filed a bid to challenge her conviction at the court of appeal, officials have said.
Letby, 33, was sentenced to life in prison after she was found guilty of murdering seven babies and the attempted murder of six other infants.
Her legal team has filed an appeal, according to the Court of Appeal Criminal Division.
Britain's biggest child serial killer was handed 14 whole life orders in August, meaning she will never leave prison.
Lucy Letby will spend the rest of her life in prisonREUTERSLetby was working at a nurse at the Countess of Chester Hospital at the time of the murders.
She injected babies with air and poisoned two with insulin at the Chester hospital, where she worked as a nurse during her mid-twenties.
News of an appeal first arose when it was revealed that a court hearing would take place on September 25, where Crown Prosecution services would decide if a retrial was needed for the six counts of attempted murder.
The original jury was unable to reach verdicts on those counts at the end of Letby's trial.
Letby received a life sentence at Manchester Crown Court, with the judge stating she showed "pre-meditation, calculation and cunning" in her actions.
However, she refused to appear in the dock to hear her sentencing.
She was sentenced on August 21.
Letby is the third woman in the UK to be given the whole-life order sentence, after Rose West and Myra Hindley.
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The child killer murdered her victims at the Countess of Chester Hospital, but now additional cases are being looked intoCHESTER STANDARD / SWNSJustice Goss condemned Letby at her sentencing: "You acted in a way that was completely contrary to the normal human instincts of nurturing and caring for babies and in gross breach of the trust that all citizens place in those who work in the medical and caring professions," he said.
An investigation has been launched into more than 4,000 babies' medical records at the two hospitals where Letby worked.
Police and medical experts fear that she may have hurt more than 30 additional infants.
Those who have been found to have suffered “unexpected and unexplained” collapses will be passed on to the police.
