The Investigator proposes to record the fetal and postnatal development of children conceived using Mitochondrial Donation (MD) and to perform expert assessment of development at 18 months (corrected for gestational age) using the internationally validated Bayley-III developmental assessment tool.

To record the fetal and postnatal development of children conceived using Mitochondrial Donation and to perform internationally validated Bayley-III developmental assessment tool at 18 months (corrected for gestational age).

The null hypothesis for this research is that children born following the use of Mitochondrial Donation (IVF) techniques have normal neurodevelopment developmental outcomes at 18 months.

Inclusion Criteria:

Women will only be eligible if they meet all of the following criteria.

• Women with confirmed mtDNA mutation
• Suitable to undergo Mitochondrial Donation as a treatment (in line with HFEA license)
• Informed Consent for the study obtained before Mitochondrial Donation treatment commences
• Ability and willingness to adhere to the protocol including evaluation schedule
• Willingness to make available information collected during pregnancy, delivery and up to the child's age of 18 months (corrected for gestational age)

Exclusion Criteria:

Women will not be eligible if they meet any of the following criteria

• Declined Mitochondrial Donation as a treatment (in line with HFEA license)
• Inability or unwillingness to adhere to the protocol including evaluation schedule
• Unwillingness to make available information collected during pregnancy, delivery and up to the child's age of 18 months (corrected for gestational age)

Women with mitochondrial disease undergoing mitochondrial donation treatment