The impact of single versus double blastocyst transfer on pregnancy outcomes: A prospective, randomized control trial.

Objective: To determine if elective single blastocyst transfer (e-SBT) compromises pregnancy outcomes compared to double blastocyst transfer (DBT) in patients with favorable reproductive potential.

Methods: This Randomized Control Trial included 50 patients with SBT (Group 1) and 50 patients with DBT (Group 2). All women were <35 years and had favorable reproductive potential. Randomization criterion was two good quality blastocysts on day 5. Patients who did not get pregnant or who miscarried underwent subsequent frozen cycles with transfer of two blastocysts (if available) in both groups.

Results: No significant difference was observed in the majority of the demographic data, infertility etiology, ovarian stimulation characteristics and embryology data between the two groups. There was a significantly lower clinical pregnancy (61.2% vs 80.0%), and delivery (49.0% vs 70.0%) rates, but no difference in implantation (59.2% vs 54.0%), miscarriage, or ectopic pregnancy rates between Group 1 and Group 2, respectively. There was a significantly higher multiple pregnancy rate in Group 2 (35.0%) compared to Group 1 (0%) [P=0.000]. When fresh and first frozen cycles were combined, there was a significantly lower cumulative clinical pregnancy (77.6% vs 96.0%, P=0.007) and delivery (65.3% vs 86.0%, P=0.016) rates in Group 1 compared to Group 2 respectively.

Conclusions: In patients with favorable reproductive potential, although e-SBT appears to reduce clinical pregnancy and live-birth rates, excellent pregnancy outcomes are achieved. Clinicians must weigh the benefits of DBT against the risk associated with multiple pregnancies in each specific patient before determining the number of blastocysts to be transferred.