Frozen blastocyst transfer reduces incidence of ectopic pregnancy compared with fresh blastocyst transfer: a meta-analysis

Ectopic pregnancy (EP) is the main cause of maternal death during early pregnancy. Blastocyst transfer (BT) reduces EP rates compared with cleavage stage embryo transfer (ET), and frozen ET reduces EP rates compared with fresh ET. However, data comparing the EP rate of fresh BT and frozen BT are limited. The objective of this meta-analysis was to determine whether frozen BT decreases the EP rate compared with fresh BT.PUBMED, EMBASE, and Cochrane Library databases were searched for papers with no limitation on language and publication year. A systemic literature search identified 14 studies which met the inclusion criteria for further analysis. EP rate is our only outcome measure. All statistical analyses were carried out using RevMan software [version 5.3]. Random effects models were chosen to calculate the odds ratio (OR).Fourteen retrospective studies (n = 251,762 cycles) were finally analyzed, including 154,214 and 97,548 cycles undergoing fresh and frozen BT, respectively. Compared with fresh BT, the frozen BT was associated with an decrease in EP rate [OR = 1.79; 95% confidence interval (CI) = 1.37-2.34, heterogeneity was 71%], the EP rate was 1.74% (2683/154,214 pregnancies) for fresh BT and 0.97% (949/97,548 pregnancies) for frozen BT. The number of embryos transferred in subgroup analysis found that the incidence of EP in frozen BT is lower than fresh BT (OR = 1.62; 95% CI = 1.38-1.91), the EP rate was 1.2% (206/16,610 pregnancies) for one fresh BT and 0.8% (153/19,569 pregnancies) for one frozen BT, also the EP rate was 1.9% (78/4043 pregnancies) for two fresh BT and 1.1% (19/1790 pregnancies) for two frozen BT.Our meta-analysis found that frozen BT was associated with an decrease in EP rate compared with fresh BT in IVF/ICSI patients. We also found that a single frozen BT is the better choice as a method to reduce the incidence of EP.