Scientists have raised fresh questions over effectiveness and safety of ‘gene-editing’ techniques which create ‘three-parent babies’. The technique aims to prevent babies inheriting health problems which may lead to developmental delays, seizures, deafness and heart failure. The 'three-parent' IVF technique creates an embryo with no disorder. Many concerns have been raised as to the ethics. Now, a report has discovered ‘potential adverse’ outcomes when using the technique: it states, ‘In some trials the transfer of unhealthy mitochondria could sometimes ‘carry-over’ and dominate the healthy mitochondria.’ This may increase over time, potentially causing one of the diseases the therapy was intended to cure, and therefore nullifying the technique’s effect. Last year, the UK legalised ‘three-parent’ IVF. The fertility regulator, Human Fertilisation and Embryology Authority (HFEA), is yet to give it the green light. HFEA will wait for further experiments on the technique’s efficiency and safety before approving it for clinical use.