Fertility clinics are offering young mitochondria in controversial fertility technique

A small number of fertility clinics around the world are offering a controversial treatment: a procedure to furnish clients’ embryos with donated mitochondria as a way to increase the chances of taking home a baby.

The method, called mitochondrial replacement therapy (MRT), involves removing the nucleus from a person’s egg or a couple’s single-cell embryo and transplanting it into an egg from a young donor. The theory — which remains unproven in rigorous clinical trials — is that the donor’s mitochondria might help the egg, once fertilized, or embryo to mature. Any resulting babies would have nuclear DNA from their biological mothers and fathers and mitochondrial DNA from the egg donor.

Scientists have already shown in a clinical trial that MRT can produce healthy children for parents whose mitochondria carry disease-causing mutations. But Nature has identified clinics in Asia, Europe and the Americas that advertise MRT to increase the success rate of in vitro fertilization (IVF) for a broader range of clients who do not have such mutations. “MRT can transform your fertility journey,” says the website of...