Awarded to Robert G. Edwards, who developed in vitro fertilization (IVF) and ushered in the era of "test-tube babies". The first child born as a result of IVF was Louise Brown, 25 July, 1978. Since that time approximately 4 million children have been born worldwide as a result of IVF techniques.
This choice may be controversial, as IVF is itself a controversial technique. It involves conception and manipulation of human embryos in the laboratory. While the technique has helped some infertile couples, the practice of manipulating human embryos has opened the way to cavalier views of nascent human life, including stockpiling "excess" human embryos, and in many ways is the precedent to the embryonic stem cell debate.
Prior to the announcement, there had been widespread speculation that this year's Nobel Prize in Physiology or Medicine might go to Shinya Yamanaka, the Japanese scientist who developed the technique of induced pluripotent stem cells (iPS cells), reprogramming normal cells to behave like embryonic stem cells, yet without the use of embryos, eggs, or cloning. Maybe next year.