Comparison of frozen-thawed embryo transfer strategies for the treatment of infertility in young women: a retrospective study

Abstract

Objective To investigate transfer strategies in the frozen-thawed embryo transfer (FET) cycle. Methods The clinical data of 1,652 FET patients were divided into five groups according to the number and quality of the transferred blastocyst: high-quality single blastocyst group (group A, n = 558), high-quality plus poor-quality double blastocyst group (group B, n = 435), poor-quality double blastocyst group (group C, n = 241), high-quality double blastocyst group (group D, n = 298), and poor-quality single blastocyst group (group E, n = 120). Inter-group comparison analyses of primary conditions, pregnancy outcomes and neonatal outcomes were then performed. Results Group A had the highest embryo implantation rate (67.38%), significantly different from the implantation rates of the other four groups. The gemellary pregnancy rate (1.60%), preterm birth rate (5.58%), neonatal birth weight (3,350g [3,000g, 3,650g]), neonatal birth age (39.57 weeks [38.71, 40.34]), and incidence of low birth weight (7.02%) in group A were different from those in groups B, C, and D, but did not significantly differ from those in group E. Moreover, the proportions of male infants born in groups A (56.86%) and D (59.41%) were significantly higher than those in the other three groups. Double blastocyst transfer (0.528, 95% CI [0.410–0.680], P < 0.001) and high-quality blastocyst transfer (0.609, 95% CI [0.453–0.820], P = 0.001) were found to be protective factors for live birth. In addition, double blastocyst transfer was also the largest risk factor for pregnancy complications (3.120, 95% CI [2.323–4.190], P < 0.001) and neonatal complications (2.230, 95% CI [1.515–3.280], P < 0.001), especially for gemellary pregnancy (59.933, 95% CI [27.298–131.58], P < 0.001) and preterm birth (3.840, 95% CI [2.272–6.489], P < 0.001). Based on the ROC curves, a double blastocyst transfer could predict gemellary pregnancy reliably with a high area under the curve (AUC = 78.53%). Additionally, a double blastocyst transfer could effectively predict a high risk of pregnancy complications (AUC = 65.90%), neonatal complications (AUC = 64.80%) and preterm birth (AUC = 66.20%). Conclusion The live birth rate of frozen-thawed high-quality single blastocyst transfer is lower than that of double high-quality blastocyst transfer, which can significantly increase the embryo implantation rate. High-quality single blastocyst transfer also significantly lowers the risk of gemellary pregnancy, preterm birth, and low birth weight, and can significantly improve maternal and infant outcomes. After weighing the pros and cons of live birth with pregnancy and neonatal complications, the authors believe that high-quality single blastocyst transfer is the optimal FET strategy for young women and is worthy of further clinical application. Despite this recommendation, high-quality single blastocyst transfer can increase the risk of monozygotic twins, as well as significantly increase the proportion of male infants born.

Comparison of pregnancy outcomes among patients of different ages who underwent frozen-thawed high-quality single blastocyst transfer

“…Age is one of the most important factors in choosing an embryo transfer strategy. A meta-analysis showed that high-quality SET is the first choice for women under 40 years of age [ 10 ], which coincides with previous studies by our team [ 4 , 5 ]. However, some studies suggest that the best pregnancy outcomes can be obtained by transferring a single blastocyst in individuals under 35 years old and 35–37 years old; while, for individuals aged 38–40 years and older, DET has better perinatal outcomes than SET [ 11 ].…”

“…Due to improvements in laboratory quality control, good culture environments and freezing technology, single blastocyst transfer (SBT) is widely used in clinical practice. Our team previously conducted a study on the number and type of blastocysts transferred and found that high-quality SBT was the optimal frozen-thawed embryo transfer (FET) strategy for young women [ 4 ]. Although this strategy is still feasible for patients aged 35–40 years [ 5 ], there were some limitations in the previous study; for example, women of advanced age were not stratified, and it is impossible to determine whether the benefits of SBT are the same for women aged 35–37 years and older.…”

Comparison of frozen-thaw blastocyst transfer strategies in women aged 35–40 years: a retrospective study

“…Interestingly, in our previous study of young women aged < 35 years, we found that the proportion of male offspring increased significantly only with high-quality SBT and high-quality DBT ( 10 ). Furthermore, several studies ( 22 , 23 ) have also concluded that high-quality blastocysts are more likely to result in male babies when compared to poor-quality blastocysts.…”

“…Currently, single blastocyst transfer (SBT) is generally used for young patients with a better prognosis; a previous study confirmed that frozen-thawed SBT is associated with a higher singleton live birth rate than fresh SBT ( 9 ). In our latest study, we found that high-quality SBT is the optimal FET strategy for young women aged < 35 years ( 10 ); however, the feasibility and efficacy of this strategy for women of advanced age has not been reported and needs to be confirmed by further studies. Therefore, in the present study, we conducted a comparative analysis of five different FET strategies to investigate the efficacy and feasibility of implementing a high-quality SBT protocol for women aged 35–40 years.…”

Effect of GnRH agonist down-regulation combined with hormone replacement treatment on reproductive outcomes of frozen blastocyst transfer cycles in women of different ages

“…The studies have shown that double embryo transfer (DET) increased the chance of clinical pregnancy and live birth compared with single embryo transfer (SET), while also increasing the risk of multiple pregnancies and preterm births ( Kamath et al, 2020 ; Long et al, 2020 ; Roberts et al, 2011 ). For young women, SET should be incorporated into clinical practice owing to the reduction in pregnancy and neonatal complications ( Ma et al, 2022 ; Wu et al, 2022 ). In women of advanced age, the recommended number of embryos to be transferred is controversial ( Ma et al, 2022 ; Tannus et al, 2017 ).…”