The luteal phase insufficiency remains pivotal to the developmental changes within the endometrium throughout the menstrual cycle. Progesterone ART supplementation, encompassing both fresh and frozen embryo transfer protocols, is firmly established, the last one representing 66.6% of all transfers in Latin America, and 56.8% globally. Significant research efforts have delved into various LPS protocols, aiming to assess their efficacy in terms of implantation rates, clinical pregnancies, miscarriage, and live birth rates. Different LPS formulations, when to start, best route of administration, dosage, and duration, and whether there is a place for additional agents are frequently discussed. In fresh embryo transfer cycles, the most prescribed LPS protocols, utilizing either micronized vaginal progesterone or dydrogesterone orally, have been extensively compared in double-blind, placebo-controlled randomized controlled trials. Various FET protocols, artificial or natural cycles, differing primarily in the presence or absence of a corpus luteum, appear to present comparable clinical pregnant rates but emerging evidence suggests a potential association between artificial cycle and elevated risks of preterm births and preeclampsia. Considerable debate and controversies persist, regarding the optimal LPS approach for different FET strategies. Progesterones in general have been used for more than 60 years and so far, no data support any first-trimester use increasing the risk of fetal abnormalities. The ultimate challenge for us physicians is to stay confident in our choices while looking for the clearest evidence-based decisions on treatment, aware that the debate must include ART and concerns about infertility and procedures per se, not just medications.