THE IMPACT OF SINGLE VS DOUBLE BLASTOCYST TRANSFER ON PREGNANCY OUTCOMES AND THE MULTIPLE BIRTH RATE: A PROSPECTIVE, RANDOMIZED CONTROL TRIAL

OBJECTIVE: To determine if single blastocyst transfer (SBT) compromises pregnancy outcomes compared to traditional double blastocyst transfer (DBT) in patients with favorable reproductive potential. DESIGN: Randomized Control Trial ISRCTN69937179. MATERIALS AND METHODS: The study (2009-13) consists of 41 patients with SBT (group 1) and 39 patients with DBT (group 2). All women were ≤35 years, had day 3 FSH levels ≤10 mIU/ml, had no history of poor ovarian response, and no more than one previous IVF failure. Randomization criterion was two good quality Day 5 blastocysts. ICSI was performed on mature oocytes and luteal phase was Supported by vaginal progesterone. Some women who did not get pregnant or who miscarried underwent subsequent frozen-thawed cycles. RESULTS: No significant difference was observed in the demographic data or infertility etiology between the groups except for mean female age and incidence of endometriosis (both significantly lower in group 1). There was no significant difference in the ovarian stimulation or embryology data between the groups. There was a significant difference in clinical pregnancy (59% vs 80%, P<0.05), and delivery/ongoing pregnancy (44% vs 67%, P<0.05) rates, but no difference in implantation (49% vs 54%), miscarriage, or ectopic rates between group 1 and group 2, respectively. There was a significantly higher multiple pregnancy rate in group 2 (33%) compared to 0% in group 1 (P<0.05). When fresh and frozen cycles were combined, there was a significant difference (P<0.05) in clinical pregnancy (71% vs 90%) and delivery/ongoing pregnancy (56% vs 77%) between group 1 and group 2 respectively. CONCLUSION: In patients with favorable reproductive potential, although SBT appears to reduce clinical pregnancy and live-birth rates, excellent pregnancy outcomes are achieved. Clinicians must weigh the benefits of DBTagainst the risk associated with multiple pregnancy in each specific patient before determining the number of blastocysts to be transferred.