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

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.

Retrospective cohort study.

Assisted reproductive technologies program at Wilford Hall Medical Center.

Patients electing for either D3ET or D5ET.

Participants meeting inclusion criteria for D5ET elected either D3ET or D5ET.

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.

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.

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.