An innovative approach to in vitro fertilization (IVF) has successfully led to the birth of a healthy lamb. This method involves maturing immature eggs in a lab setting and marks a significant milestone in reproductive technology for large animals. The implications of this study may increase the availability and success rates of IVF treatments for women facing infertility issues, particularly those with ovaries compromised by cancer therapies.

“This is a monumental advancement,” says Stein Christensen, a professor at Copenhagen University Hospital who was not part of the research.

This study builds on over three decades of previous research, which first showed the potential of IVF in mice, as outlined in this live birth study. “Reproductive processes in sheep are more comparable to humans than in mice,” explains Dr. Manjushree Boob, whose clinic in Maharashtra, India, was not involved in the research.

Conventional IVF requires a series of daily hormone injections for one to two weeks that stimulate immature eggs to mature in the ovaries. Typically, only about 6 to 8 out of 10 mature eggs fertilize successfully, leading to implantation challenges, with only a 20% success rate for live births.

Due to these low success rates, attention is turning to the potential of utilizing immature eggs. Women are born with hundreds of thousands of eggs, but this count declines throughout their lives. Each menstrual cycle sees the maturation of a single follicle that releases an egg during ovulation.

In recent research, Helen Picton and her team at the University of Leeds collected numerous immature follicles from sheep. They utilized a blend of reproductive hormones and growth factors, such as follicle-stimulating hormone, to promote growth and maturation, achieving approximately 60% maturation of the eggs.

About 30% of these matured eggs were successfully fertilized, leading to embryos implanted in 18 sheep. This resulted in the birth of a female lamb in early 2024, along with four additional lambs earlier this year. Notably, the female lamb has also given birth to two offspring this year. Mr. Picton shared these findings at the European Society of Human Reproduction and Embryology conference in London on July 7th.

The outcomes of this research suggest that this novel technique could significantly enhance egg availability for fertilization and improve conception rates, as noted by Christensen. However, it may need to complement standard IVF practices, which could complicate the process and lead to higher costs.

Picton pointed out that while this approach shows promise, it is unlikely to become standard practice due to the invasive nature of follicle retrieval, which is more complicated than collecting mature eggs through conventional IVF.

Nonetheless, this method could greatly assist women whose ovaries have been adversely affected by cancer treatments. While doctors typically remove and freeze ovarian tissue to preserve fertility before treatment, this process carries risks, including the possibility of reintroducing cancer cells during transplantation. Picton emphasized that retrieving immature eggs poses fewer risks, as cancer primarily affects surrounding tissues.

Before widespread use, further research is necessary to determine if human eggs matured using this method are viable for fertilization. Christensen stated that upcoming studies are expected in the next few years, and, if they yield positive results, small-scale trials could aim for healthy live births. However, obtaining ethical approval may take 5 to 10 years. It is crucial that such studies demonstrate that benefits clearly outweigh any associated risks for future parents and their children.