Background
The number of re-biopsied blastocysts is widely increasing in PGT cycles and concerns regarding retesting, which involve double biopsy and vitrification-warming, have been raised. The re-biopsy intervention seems to significantly reduce the pregnancy potential of a blastocyst but the evidence is still restricted to retrospective observational studies reporting a low number of cycles with re-biopsied embryos. Additionally, the neonatal outcomes after the transfer of re-biopsied and re-vitrified embryos are poorly documented to date.
Methods
A systematic review, using PubMed/Medline, EMBASE, Cochrane Central Register of Controlled Trials, Scopus, Web of Science and Google Scholar to identify all relevant RCTs, cohort and case-control studies published until December 2024. The participants will include women undergoing preimplantation genetic testing and single euploid FET cycles. The primary outcomes are live birth rate (LBR) and singleton birthweight, whereas secondary outcomes are post-warming embryo survival rate, clinical pregnancy (fetal heart pregnancies at 4.5 weeks), miscarriage rate (loss of pregnancy before the 20th week, and stillbirth), preterm birth (PB) rate, small-for-gestational age (SGA, <-1.28 SDS), large-for-gestational age (LGA, >+1.28 SDS), low birthweight (LBW; birthweight < 2500g), preterm birth (gestation < 37 weeks), macrosomia (birthweight > 4000g), pre-eclampsia, eclampsia, perinatal death and major congenital malformations. Eligible studies will be selected according to pre-specified inclusion and exclusion criteria. Additionally, manual search will target other unpublished reports and supplementary data. At least two independent reviewers will be responsible for article screening, data extraction and bias assessment of eligible studies. A third reviewer will resolve any disagreements. The Newcastle-Ottawa scale and will be used to assess the quality of the included studies. Studies that receive a score equal to or greater than 7 on the NOS will be considered high quality. The extracted data will be pooled and a meta-analysis will be performed. To carry out the data synthesis, a random effects meta-analysis will be conducted using the RevMan software. Heterogeneity will be evaluated by Cochran’s Q test and the I2 statistics and the strength of evidence will be rated with reference to GRADE. The review and meta-analysis will be reported according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines.
Discussion
The findings of this systematic review will be important to clinicians, embryologists, patients, and assisted reproductive service providers regarding the decision-making on retesting embryos for PGT in FET cycles.
Systematic review registration:
PROSPERO CRD42024498955
