Embryo Culture Conditions: What Embryos Like Best In London this May, there will be an unusual event: the

celebration of two million children delivered after in vitro fer-tilization (IVF) procedures. The first “test tube ” baby, Louise Brown, was born on 25 July 1978, demonstrating for humans what had already been shown for the mouse and the rabbit, namely that an oocyte could be fertilized by sperm in vitro, transferred to the reproductive tract, and establish a successful pregnancy. By the mid-1980s there were a few hundred IVF children, mostly conceived at Bourne Hall, near Cambridge, where Patrick Steptoe, who retrieved the eggs, and Robert Edwards, the embryologist and human IVF pioneer, estab-lished their clinic and research laboratory. What was originally labeled as “immoral, unethical and dehumanizing