Lab-Grown Eggs Lead to Healthy Lambs in Fertility Win

For the first time ever, researchers have created healthy lambs from eggs that matured completely outside the body, opening new doors for people facing fertility challenges.

A team at the University of Leeds successfully grew immature eggs into mature ones in the lab, then used them to create five healthy lambs through IVF. The first lamb, born in early 2024, has already grown up and given birth to two healthy babies of her own this year, proving the technique works across generations.

The breakthrough matters because sheep reproduction closely mirrors human reproduction, far more than mice studies that showed promise 30 years ago. Women are born with hundreds of thousands of immature eggs, but traditional IVF can only access about 10 mature eggs per cycle, leading to successful pregnancies just 20 percent of the time.

The researchers collected tiny follicles containing immature eggs from sheep ovaries and bathed them in a special mix of hormones and growth factors. About 60 percent matured into healthy eggs, and roughly 30 percent of those were successfully fertilized and implanted.

The technique could be especially valuable for women whose ovaries have been damaged by cancer treatment. Right now, doctors freeze ovarian tissue before chemotherapy and transplant it back later, but that carries a risk of reintroducing cancer cells. Growing eggs from immature follicles would eliminate that danger since cancer typically affects only surrounding tissue.

Experts not involved in the research are calling it a major breakthrough. "Much more than mice, reproduction in sheep is quite similar to in the human body," says Dr. Manjushree Boob, a fertility specialist in India.

The Ripple Effect

This discovery could transform fertility treatment for millions worldwide. By dramatically increasing the number of viable eggs available for fertilization, it may boost conception rates for couples who have struggled with standard IVF. The approach offers particular hope for young cancer survivors who want to start families after beating their disease.

Human trials are still years away. Researchers need to first confirm that human eggs can mature and be fertilized using this method, which should happen within the next few years. If those studies succeed, small clinical trials could begin in five to 10 years, pending ethical approval to ensure the technique is safe for parents and children.

The breakthrough won't replace standard IVF for most people since collecting immature eggs requires removing ovarian tissue, a more invasive procedure than current methods. But for those with limited options, it could be life changing.