The prevalence of late-follicular phase progesterone elevation and impact on the ongoing pregnancy rate after fresh and frozen blastocyst transfer. Sub-study of an RCT. - Stormlund, Sacha; Sopa, Negjyp; Lyng Forman, Julie; Zedeler, Anne; Bogstad, Jeanette; Prætorius, Lisbeth; Nielsen, Henriette Svarre; Klajnbard, Anna; Englund, Anne Lis; Ziebe, Søren; Freiesleben, Nina la Cour; Bergh, Christina; et al. (Human Fertility, 2024)