Georgia Reproductive Specialists in Atlanta, GA was one of 25 sites nationwide that recently completed the largest in vitro fertilization (IVF) clinical trial ever in the world. The landmark trial of 1,211 women evaluated ENDOMETRIN(R) (progesterone) Vaginal Insert, 100 mg, a progesterone supplement used in patients undergoing assisted reproductive technology (ART) treatment. Progesterone is necessary to support embryo implantation and early pregnancy.