In October 2007, a British woman whose eggs were matured in a lab rather than her body gave birth to healthy twins, marking the U.K. debut of a procedure that could spare women using assisted reproduction from potentially dangerous fertility drugs.

During in vitro fertilization—IVF, the standard assisted-reproduction technique—women take drugs to stimulate egg production and maturation. The eggs are then harvested, fertilized, and implanted. The drugs, however, sometimes cause a condition called ovarian hyperstimulation syndrome, which in rare cases can be life-threatening.

During in vitro maturation, or IVM, immature eggs are removed and nurtured in a lab before being fertilized and implanted. Only one dose of fertility drugs is required.

The technique is still immature: The BBC reports that, of 2 million children born worldwide through IVF, around 400 were produced through IVM; success rates of lab-matured eggs are currently lower than those used in IVF. But for women who are especially sensitive to fertility drugs, or want to freeze eggs for future use, IVM may be a good option.