Removal of lysed blastomeres from frozen–thawed embryos improves implantation and pregnancy rates in frozen embryo transfer cycles

Objective

To evaluate the effect of degenerated (lysed) blastomere removal on implantation and pregnancy rates in cleavage-stage cryo–embryo transfer (ET) cycles.

Design

Randomized clinical trial.

Setting

Private reproductive medical center.

Patient(s)

A total of 88 patients who received frozen–thawed ET, divided into two groups.

Intervention(s)

Embryo freezing and thawing; opening of the zona pellucida and removal of cryodamaged blastomeres (in the study group), followed by same-day ET.

Main Outcome Measure(s)

Extent of survival of cleavage-stage embryos after the freeze–thaw procedure; embryo implantation and clinical pregnancies.

Result(s)

Oocyte number per patient, fertilization rate, embryo development rate (and quality), and freezing rates were similar in the two groups in the fresh cycle. In the control group, a total of 55 embryos (25%) of the 217 thawed remained fully intact, and 53 (26%) of the 207 in the study group remained intact. The average number of embryos transferred per group was similar (control, 3.4 ± 0.9; study, 3.3 ± 0.9). Implantation rates were 12% and 26% in the control and study groups, respectively. The clinical pregnancy rate was 23% in the control group and 64% in the study group when lysed cell removal was performed.

Conclusion(s)

The results show that pregnancy and implantation rates are higher in the study group; therefore, the removal of degenerated blastomeres may be beneficial to all patients who undergo cleavage-stage, frozen–thawed ET.

Key Words:  Assisted hatching , cryopreservation , embryo , implantation , pregnancy