School of Animal and Microbial Sciences, University of Reading, Reading RG6 6AJ, United Kingdom; Centre for Integrated Systems Biology and Medicine, School of Biomedical Sciences, University of Nottingham Medical School, Nottingham NG7 2UH, United Kingdom; and Department of Obstetrics and Gynecology, St. George's Hospital, London SW17 0QT, United Kingdom (At 2003-04-25)