Abbreviations: ACOG: American College of Obstetricians and Gynecologists; CPG: clinical practice guideline or guidance; DCOI: declaration of conflict of interests; NICE: National Institute of Health and Care Excellence; NHLBI: National Institutes of Health, National Heart, Lung, and Blood Institute; PGD: Preimplantation genetic diagnosis; and RCOG: Royal College of Obstetricians and Gynaecologists.