The United Kingdom is now the first country to legalize mitochondrial DNA transfers.

Earlier in February, the legislation passed the House of Commons by a vote of 282-12. It moved to the House of Lords, which passed it by a majority of 232. Clinical trials on humans could begin as early as the end of 2015.

There’s a lot of support for three-person in vitro fertilization: Mothers pass along mitochondrial DNA as well as nucleic DNA to their babies, while fathers only pass along nucleic DNA. Mitochondrial DNA doesn’t carry information about character traits, but does carry certain diseases that can be life-threatening. Mothers can avoid passing along those diseases by using a donor’s mitochondrial DNA instead, which is combined with the mother and father’s nucleic DNA to form a healthy embryo.

The conversation about three-parent IVF has taken place in the United States, but no formal regulation has been applied to the procedures.

Read our feature from earlier this month to learn more about the procedures and the ethical questions it poses.