Impact of day 3 or day 5 embryo transfer on pregnancy rates and multiple gestations.

OBJECTIVE: To test the hypothesis that day 5 ET (D5ET) is superior to day 3 ET (D3ET) in pregnancy outcome and that it also reduces multiple gestations. DESIGN: Retrospective cohort study. SETTING: Assisted reproductive technologies program at Wilford Hall Medical Center. PATIENT(S): Patients electing for either D3ET or D5ET. INTERVENTION(S): Participants meeting inclusion criteria for D5ET elected either D3ET or D5ET. MAIN OUTCOME MEASURE(S): Cycles were compared by day of transfer and further stratified by patient age (<35 years and 35-40 years). The number of oocytes retrieved, embryos on day 3, embryos transferred, pregnancy rate, implantation rate, and twin and high order multiples (>or=triplets) rates were compared. RESULT(S): Of the 274 patients who met our inclusion criteria, 153 underwent a D3ET and 121 underwent a D5ET. The D5ET group had a significantly lower mean age and number of embryos transferred and a higher implantation rate (56% vs. 42%) than the D3ET group. Patients who were 35-40 years old had a significantly higher live-birth rate (68% vs. 40%). Although not statistically significant, the D5ET groups had higher clinical pregnancy (73% vs. 65%) and twin pregnancy (33% vs. 25%) rates. CONCLUSION(S): Blastocyst transfer resulted in fewer embryos transferred, with a trend toward improved clinical pregnancy and higher twin pregnancy rates. Live-birth rates were improved in patients 35-40 years of age. Younger patients opting for D5ET should do so with a commitment toward single ET.