A woman wants to use her daughter's frozen eggs to give birth to her own grandchild.
Her daughter was desperate to have children and apparently asked her mother to "carry my babies" before she died of cancer in 2011.
The 60-year-old mother is appealing to the Court of Appeal to allow her to proceed after losing a High Court case last year.
An independent regulator has so far refused to allow the woman and her husband to take their daughter's eggs to a US fertility clinic to be used with donor sperm.
Her QC, Jenni Richards, told judges on Wednesday that the woman simply wants to fulfill her daughter's wishes, saying she would have been "devastated" if she had known her eggs would not be used.
Ms Richards said the "inevitable" consequence would be that the eggs "will simply be allowed to perish".
However, the Human Fertilisation and Embryology Authority (HFEA) said the eggs cannot be released as the dying woman did not give full written consent before she died.
Catherine Callaghan, counsel for the HFEA, argued:
If the appeal is successful, her mother could become the first person in the world to become pregnant using a dead daughter's eggs.