PurposeThe objective of this study was to assess if very-low-dose Lupron (VLDL) and ultra-low-dose Lupron (ULDL) protocols can have comparable cycle outcomes when compared to other "poor responder" stimulation protocols based on POSEIDON classification groups 3 (PG3) and 4 (PG4).MethodsA retrospective cohort study at a single, large academic center was performed. Women in PG3 (age < 35, AMH < 1.2 ng/mL) or PG4 (age >= 35, AMH < 1.2 ng/mL) undergoing in vitro fertilization using an ULDL (Lupron 0.1 to 0.05 mg daily), VLDL (Lupron 0.2 to 0.1 mg daily), microflare (Lupron 0.05 mg twice a day), estradiol priming/antagonist, antagonist, or minimal stimulation protocols from 2012 to 2021 were included. The primary outcome was the number of mature oocytes (MII) obtained. The secondary outcome was live birth rate (LBR).ResultsThe cohort included 3601 cycles. The mean age was 38.1 +/- 3.8 years. In the PG3 group, ULDL and VLDL protocols produced a comparable number of MIIs (5.8 +/- 4.3 and 5.9 +/- 5.4, respectively) and live births (33.3% and 33.3%, respectively) when compared to other protocols. In the PG4 group, ULDL and VLDL protocols resulted in a higher percentage of MIIs when compared to microflare or minimal stimulation (Microflare/ULDL: adjusted relative risk (aRR) 0.78 (95% CI 0.65, 0.95); min stim/ULDL: aRR 0.47 (95% CI 0.38, 0.58); microflare/VLDL: aRR 0.77 (95% CI 0.63, 0.95); min stim/VLDL: aRR 0.47 (95% CI 0.38, 0.95)). There were no significant differences in LBR.ConclusionDilute Lupron downregulation protocols have comparable outcomes to other poor responder protocols and are reasonable to use.