[1] UCL, EGA Inst Womens Hlth, Fac Populat Hlth Sci, London, England
[2] Hackensack Meridian Sch Med, Nutley, NJ USA
[3] Liverpool Womens Hosp NHS Fdn Trust, Liverpool, England
[4] Chinese Acad Med Sci & Peking Union Med Coll, Peking Union Med Coll Hosp, Dept Obstet & Gynecol, Natl Clin Res Ctr Obstet & Gynecol Dis, Beijing, Peoples R China
[5] Monash Univ, Dept Obstet & Gynaecol, Clayton, Vic, Australia
[6] Ectopic Pregnancy Trust, London, England
[7] Univ Hosp Chieti, Ctr Fetal Care & High Risk Pregnancy, Dept Obstet & Gynecol, Chieti, Italy
[8] Univ Med & Pharm Ho Chi Minh City, Dept Obstet & Gynecol, Ho Chi Minh City, Vietnam
[9] Monash Hlth, Monash Womens, Clayton, Vic, Australia