The U.K. could become the first country to legalize the production of a human embryo from three donors. Here, the freezing platform for an embryo, top, also known as a straw, is seen at an in vitro fertilization lab. Jim Stevens/MCT/Landov hide caption

itoggle caption Jim Stevens/MCT/Landov

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