Affiliation: | a Biostatistics and Clinical Epidemiology Service, Clinical Center, National Institutes of Health, Bethesda, Maryland b Reproductive Biology and Medicine Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland c Nuffield Department of Obstetrics and Gynaecology, University of Oxford, Oxford, United Kingdom d Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom |