Mutations in mitochondrial (mt) DNA are maternally inherited and can cause fatal or debilitating disorders without effective treatments. 1,2 The severity of clinical symptoms is often associated with the mtDNA mutation load in heteroplasmy. 3 Experimental nuclear transfer in metaphase II (MII) spindle oocytes or in pronuclear (PN) zygotes, also called mitochondrial replacement therapy, has been shown to be a novel technology in minimizing mutated mtDNA transmission from oocytes to pre-implantation embryos. 4,5 Here we report the first live birth of a boy following spindle nuclear transfer (SNT).