Abstract
Research questionWhat is the clinical importance of vitrified-warmed blastocyst transfer timing if performed on days 5, 6 and 7 after detecting the LH surge using urine tests? DesignBetween 2013 and 2019, 2080 vitrified-warmed blastocyst transfers in a true natural cycle were performed and later analysed at the Department of Reproductive Medicine, University Medical Centre Maribor, Slovenia. Urine LH tests were performed twice daily to monitor the onset of the LH surge. Vitrified-warmed blastocyst transfer (frozen embryo transfer [FET]) was performed on day 5 (group 1), 6 (group 2) or 7 (group 3) after the LH surge in 18%, 77% and 4% of cycles, respectively. The patient and cycle characteristics among the groups were compared using the Cochran–Mantel–Haenszel test and respective generalized linear mixed models. Propensity score matching was used to adjust for potential differences among the groups. ResultsThere were no statistically significant differences between groups 1, 2 and 3 in the cycle and patient characteristics, clinical pregnancy rate (38% versus 39% versus 31%), implantation rate (34% versus 36% versus 31%), miscarriage rate (7% versus 9% versus 7%) and delivery rate (31% versus 31% versus 24%). The day of FET after the LH surge detected using a urine test was not significantly associated with live births. ConclusionsThe results of the current study suggested that the vitrified-warmed blastocyst transfer could be scheduled on day 5, 6 or 7 after a positive LH urine test without having a significant impact on the clinical outcome.
Highlights
In recent years, vitrified-warmed blastocyst transfer (FET) has become an important part of the in vitro fertilisation program
This study aimed to establish whether the clinical outcomes of vitrified-warmed blastocyst transfer were comparable if Frozen embryo transfer (FET) was performed on days 5, 6, and 7 after the luteinising hormone (LH) surge detection using urine tests
The number of blastocysts transferred in all groups was the same; the proportion of difficult embryo transfers, transferred blastocysts vitrified on day 5, and the proportion of morphologically optimal blastocyst transfers did not differ among the cycles with FET on days 5 and 6 and day 7 after the LH surge(Table 1).Patients undergoing a FET on day 5, 6 or 7 after the LH surge showed no statistically significant differences concerning clinical pregnancy rate, implantation rate, miscarriage rate, and live birth rate (Table 2).Propensity score matching was performed using age, the number of transferred embryos and blastocyst quality to account for potential differences among the groups (Figure 1); the Cochran–Mantel– Haenszel test was used again to compare FET cycle outcomes between the respective groups
Summary
In recent years, vitrified-warmed blastocyst transfer (FET) has become an important part of the in vitro fertilisation program. Elective single embryo transfer and freeze-all strategy, together with advanced cryopreservation techniques, provide important benefits for the patients and primarily improve the safety of the treatment and a higher cumulative live birth rate. Various endometrial preparation strategies have been introduced to optimise the success of FET; the optimal method has not yet been established. The most frequently used cycle regimens include a natural ovulatory cycle protocol with luteinising hormone (LH) detection (true natural cycle, tNC), human chorionic gonadotropin application (modified natural cycle, mNC) and the artificial cycle. The benefit of NC FETs is to avoid medication and the disadvantage is a need for the precise monitoring and limited flexibility during the timing of FET (Reljič and Knez, 2018)
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