Levi-Setti PE, et al. - Researchers in this study sought to assess whether there is a difference in implantation and pregnancy rates between embryos transferred electively at cleavage or blastocyst stage in infertile women ≤ 38 years with at least four zygotes on day 1 post retrieval. In the selected group of patients, fresh blastocyst-stage transfer vs cleavage-stage transfer indicated no significant difference in terms of implantation and pregnancy rate. Both groups showed a high twin delivery rate (35.59%), and although not significant, the rates were higher in the blastocyst transfer group (42.59 vs 28.12%). As per findings, they suggested considering single embryo transfer (SET) policy, even in cleavage stage in patients younger than 39 years with at least four zygotes.

Methods

• Researchers performed a randomized clinical trial in a single tertiary care hospital with a sample size of 194 patients in each arm for a total population of 388 women.
• They included patients less than 39 years of age with more than three fertilized oocytes and less than four previous assisted reproductive technology (ART) attempts.

Results

• In terms of age, years of infertility, indication to treatment, basal antimüllerian hormone and FSH, number of previous ART cycles, primary or secondary infertility, type of induction protocol, days of stimulation, total gonadotrophin dose, and estradiol (E2) and progesterone (P) levels at trigger the groups were similar.
• Researchers recognized no statistically significant differences in terms of number of retrieved oocytes, inseminated oocytes, fertilization rate, canceled transfers (7.73% in blastocyst and 3.61% in cleavage stage group), and cycles with frozen embryos and/or oocytes.
• Despite a higher number of fertilized oocytes in the blastocyst stage group (6.18 ± 1.46 vs 5.89 ± 1.54, p=0.052), a statistically higher number of embryos/randomized cycle were transferred at cleavage stage (1.93 ± 0.371) compared with the number of transferred blastocysts (1.80 ± 0.56), probably due to the number of embryos not reaching blastocyst stage (3.09%).
• The blastocyst and cleavage stage groups were not significantly different regarding the implantation rate (28.37 vs 25.67%), pregnancy rate per cycle (36.06 vs38.66%), transfer (39.66 vs 40.11%), spontaneous abortions (19.72% vs 12.00%), delivery rate per cycle (27.84 vs 32.99%), and transfer (30.17 vs 34.22%).
• The blastocyst stage group indicated higher twin delivery rate, although the difference was not significant (42.59 vs 28.12%).
• The two groups were not markedly different in terms of mean numbers of frozen blastocyst (2.30 ± 1.40 vs 2.02 ± 1.00) and frozen oocytes (7.09 ± 3.55vs 6.79 ± 3.26).