Gelson E, Gatzoulis M A, Steer P, Johnson M R
Academic Department of Obstetrics and Gynaecology, Imperial College London, Chelsea and Westminster Hospital, London, UK.
BJOG. 2009 Apr;116(5):609-11. doi: 10.1111/j.1471-0528.2008.02082.x. Epub 2009 Feb 10.