In the technique known as intracytoplasmic sperm injection, a fertility specialist uses a tiny needle to inject sperm into an egg cell. Mauro Fermariello/Science Source hide caption

itoggle caption Mauro Fermariello/Science Source

Along with sperm, the in vitro procedure adds fresh mitochondria extracted from less mature cells in the same woman's ovaries. The hope is to revitalize older eggs with these extra "batteries." But the FDA still wants proof that the technique works and is safe. Chris Nickels for NPR hide caption

itoggle caption Chris Nickels for NPR

A doctor uses a microscrope to view a human egg during in vitro fertilization (IVF), which is used to fertilize eggs that have been frozen. Mauro Fermariello/ScienceSource hide caption

itoggle caption Mauro Fermariello/ScienceSource

Sperm are placed inside the egg with a needle during a fertility treatment called intracytoplasmic sperm injection. iStockphoto hide caption

itoggle caption iStockphoto

Nurses tend newborns at Sloane Hospital for Women in New York City. Pat Carroll/Getty hide caption

itoggle caption Pat Carroll/Getty

Tina Nevill of Essex, England, holds Poppy, who was conceived by in vitro fertilization. The U.K.'s health system records all IVF cycles performed in the country. Barcroft Media/Landov hide caption

itoggle caption Barcroft Media/Landov

Human embryos under a microscope at an IVF clinic in La Jolla, Calif. Sandy Huffaker/Getty Images hide caption

itoggle caption Sandy Huffaker/Getty Images