Luteal phase supplementation after gonadotropin-releasing hormone agonist trigger in fresh embryo transfer: the American versus European approaches.

The challenges in attaining an adequate luteal phase after GnRH agonist (GnRHa) trigger to induce final oocyte maturation have resulted in different approaches focused on rescuing the luteal phase insufficiency so that a fresh transfer can be carried out without jeopardizing IVF outcomes. Over the years, two different concepts have emerged: intensive luteal support with aggressive exogenous administration of E2 and P; and low-dose hCG rescue in the form of a small dose of hCG either on the day of oocyte retrieva or on the day of GnRHa trigger (the so called "dual trigger"). Both approaches have been shown to be effective in achieving pregnancy rates similar to those obtained after conventional hCG trigger and resulting in a very low risk of ovarian hyperstimulation syndrome (OHSS). Although the idea of freezing all embryos after GnRHa trigger and transferring them in a subsequent frozen-thawed cycle has been gaining momentum, a fresh transfer leading to the live birth of a healthy child is currently considered to be the goal of IVF treatment.