Equivalency of in vitro fertilization success rates in elective single blastocyst transfer and elective double blastocyst transfer: An example of equivalence methodology in clinical reproductive health

Context: When comparing success rates between treatments, it is more appropriate to structure analyses in terms of equivalence rather than traditional analyses that assess differences. Unfortunately, no studies of elective single blastocyst transfer (eSBT) have been conducted in this manner. Aims: The objective of this study was to assess clinical equivalence of in vitro fertilization success rates among patients undergoing eSBT. Settings and Design: A historical prospective study was conducted at a private fertility center. Methods: Medical records were reviewed to identify patients eligible for eSBT. Equivalency of success rates, defined as no more than a 10% difference based on 95% confidence intervals (CIs), was compared between eSBT (n = 125) and eDBT (n = 213) groups. Results: Using traditional analysis techniques, no differences in pregnancy or live-birth rates were seen (eSBT: 84.6% vs. eDBT: 84.5%, P = 0.99; eSBT: 65.3% vs. eDBT: 72.3%, P = 0.23). The 95% CI around the difference in pregnancy rates ranged from -7.9 to 8.1, suggesting clinically equivalent pregnancy rates. Clinical equivalence was not established for live-births (95% CI = -18.5-4.5). Conclusions: Findings suggest comparable pregnancy rates can be achieved in a clinical setting when utilizing eSBT in good-prognosis patients. Although live-birth rate equivalence was not demonstrated, it is thought the additional complications associated with multiple gestations outweigh the potentially higher live-birth rate. The present study highlights the importance of utilizing equivalence analyses when making statements regarding the similarity of two treatments in reproductive health, rather than relying on superiority analyses alone.