OBJECTIVE To compare IVF data and outcomes between a standard protocol and a luteal phase E(2) protocol. DESIGN Retrospective cohort analysis. SETTING(S) Large academic assisted reproduction technologies center. PATIENT(S) Fifty-seven infertile patients with a history of poor response to IVF stimulation and 228 matched control patients. INTERVENTION(S) IVF with a standard protocol or a luteal phase E(2) protocol. MAIN OUTCOME MEASURE(S) Live-birth rates. RESULT(S) Patients in the luteal E(2) protocol required more days of stimulation and total gonadotropins and had higher peak E(2) levels when compared with the control group. The luteal E(2) protocol showed a greater percentage of embryos with >or=7 cells on day 3. A trend toward improved delivery rates was seen in the luteal E(2) protocol (28.1% vs. 22.4%; relative risk, 1.25, 0.78-2.03). CONCLUSION(S) A luteal E(2) protocol results in improved day 3 embryo development as demonstrated by the percent of embryos at the >or=7-cell stage. Likewise, the luteal E(2) protocol may ultimately improve pregnancy outcomes for patients with poor response to IVF stimulation.