Experimental IVF Produces Five Lambs From Immature Sheep Eggs

Five sheep have been born through an experimental form of IVF that matures immature eggs in the laboratory, @NewScientist reported. One of the five later produced two offspring of its own. Helen Picton at the University of Leeds led the work.

Researchers collected dozens of follicles from sheep and bathed them in a mix of reproductive hormones and growth factors. About 60 per cent of the follicles developed into mature eggs, and roughly 30 per cent of those eggs were fertilised to create embryos. The embryos were placed into the uteruses of 18 sheep.

The first female lamb arrived in early 2024, followed by four more births in 2025 or 2026. Picton presented the results on 7 July at the European Society of Human Reproduction and Embryology conference in London. Standard IVF uses daily hormone injections for one to two weeks to produce around 10 mature eggs, of which six to eight are typically fertilised, leading to a live birth in about 20 per cent of cases.

Women are born with hundreds of thousands to more than one million immature eggs. The same method produced live births in mice more than 30 years ago. Picton noted that retrieving follicles requires a sample of ovarian lining and is more invasive than standard egg collection.

She said the approach could help women whose ovaries were damaged by cancer treatment, because it avoids transplanting tissue that might contain cancer cells. Further studies are needed to determine whether human eggs matured this way can be fertilised.

Those trials are expected within the next few years, according to Stine Kristensen at Copenhagen University Hospital, who was not involved in the research.