Luteal phase serum progesterone levels after GnRH-agonist trigger - how low is still high enough for an ongoing pregnancy?

In the past years, individualization of assisted reproductive technique (ART)-treatment is increasingly common to customize the treatment protocol to the patient's specific conditions. The use of GnRH-agonist for final oocyte maturation in a gonadotropin-releasing hormone (GnRH)-antagonist protocol is the best approach to reduce the risk for ovarian hyperstimulation in high responder patients. However, due to severe luteolysis, the reproductive outcome with this approach in combination with the use of vaginal progesterone as luteal phase support, was poor. Cycle segmentation as alternative to a fresh transfer requires embryo freezing which might not be applicable to all patients due to various reasons. The concept of luteal coasting monitors the progesterone-level closely and human chorionic gonadotropin (hCG) for rescue of the corpora lutea is administered when the progesterone-level drops below a certain threshold. However, the lower range of progesterone levels in the early luteal phase after GnRH-agonist trigger, which is compatible with achieving and maintaining a pregnancy, is unknown. This case-series demonstrates, that ongoing pregnancies can be achieved even with a progesterone-level below 15 ng/ml in the early luteal phase with the timely administration of an hCG-rescue bolus. With the concept of luteal coasting, individualization of the luteal phase support according to the patient's specific luteolysis pattern is possible.