From live birth to live birth: a strong correlation between the outcomes of first and second frozen-thawed euploid blastocyst transfers from sibling oocytes.

Purpose: To investigate any correlation between the outcomes of the first euploid frozen-thawed blastocyst embryo transfer (FBT) and the subsequent euploid FBT derived from sibling oocytes.

Methods: This retrospective study analyzed data from 1051 women who underwent preimplantation genetic testing for aneuploidy and had a euploid FBT. Of these patients, 159 underwent a second transfer. The primary outcome was the live birth rate.

Results: Overall, 159 women who underwent a second euploid FBT were categorized into two subgroups depending on the implantation success of the first FBT. Of these patients, 94 (59.1%) belonged to the nonclinical group, signifying a negative result or a biochemical pregnancy. The remaining 65 (40.9%) patients belonged to the clinical group, indicating either a miscarriage or a live birth. In the binary logistic regression analysis, the live birth outcome during the first euploid FBT was a statistically significant and independent predictor of live birth in the subsequent FBT [odds ratio 4.14, 95% confidence interval (1.184-14.531), p < 0.026). Miscarriages, including those that occurred before intracytoplasmic sperm injection and in the first euploid FBT, reduced the live birth rate by approximately 34% (p < 0.027). No significant difference in the miscarriage rate was found between the two subgroups (19.2% (10/52) vs. 25.4% (14/55), p = 0.38).

Conclusion: The live birth outcome of the second euploid FBT is mainly determined by the live birth outcome of the first. Miscarriages that occurred before in vitro fertilization negatively affect the live birth outcome.