Does Maternal Age at Retrieval Influence the Implantation Potential of Euploid Blastocysts?

摘要

The average age of first-time mothers continues to rise steadily on a global scale. Concerningly, maternal age is a critical factor when determining the probability of conception either naturally or through in vitro fertilization. Two significant factors contributing to the decline in fertility with increasing age are decreased number of oocytes and increased oocyte aneuploidy in older women. However, studies have shown that even when selecting for only euploid embryos, women 35 years or older experienced significantly lower delivery rates compared with women younger than 35 years. This retrospective cohort study aimed to determine the effect of maternal age at euploid blastocyst retrieval on implantation potential. Data were gathered on autologous frozen-thawed embryo transfer (FET) cycles of euploid blastocysts that occurred between January 2013 and December 2016. Cycles were divided into 5 groups based on maternal age at retrieval: younger than 35, 35 to 37, 38 to 40,41 to 42, and older than 42 years. Blastocysts were divided into 4 groups based on morphological quality before biopsy: excellent (3-6AA), good (3-6AB, 3-6BA), average (2-6BB), and poor (3-6 BC, 3-6CB, 3-6CC). Embryos that reached blastocyst stage on day 5 were biopsied that day, whereas the others were biopsied on day 6 only if they developed into blastocysts. Specimens from selected embryos were analyzed by preimplantation genetic screening. Primary outcomes of the study were live birth rate (LBR) and implantation rate (IR). The secondary outcome was spontaneous abortion rate. Odds ratios were calculated with 95% confidence intervals and controlled for various confounding factors including blastocyst grading and day of trophectoderm biopsy (day 5 or 6). The final study cohort included 785 FET cycles in which 870 blastocysts were transferred. The cohort was divided into the 5 age groups as follows: younger than 35 (n - 227), 35 to 37 (n = 228), 38 to 40 (n = 185), 41 to 42 (n = 103), and older than 42 (n = 42) years old. Blastocyst determined to be excellent-quality were associated with significantly higher LBR compared with good-quality (78.8% vs 63.8%, P = 0.03), average-quality (78.8% vs 52.2%, P = 0.001), and poor-quality (78.8% vs 28.3%, P < 0.001) blastocysts. Embryos determined to be poor-quality were associated with a significantly lower LBR than good-quality (28.3% vs 63.8%, P < 0.001) and average-quality (28.3% vs 54.2%, P < 0.001) embryos. Excellent-quality blastocysts were associated with a significantly higher IR than average- and poor-quality blastocysts. Poor-quality embryos were associated with a significantly higher SAB rate compared with average-quality (25.0% vs 9.0%, P = 0.003), good-quality (25.0% vs 6.9%; P = 0.01), and excellent-quality (25.0% vs 2.4%; P = 0.01) embryos. Embryos biopsied on day 5 had higher LBR (60.0% vs 46.6%, P < 0.001) and higher IR (63.9% vs 47.8%, P < 0.001) compared with those biopsied on day 6. The SAB rate did not significantly differ between day 5 and day 6 embryos. Embryos biopsied on day 5 had significantly higher percentages of excellent- and good-quality blastocysts compared with those biopsied on day 6 (P < 0.001). The 5 age groups had nonsignificant differences in IR, LBR, and SAB. Older women were found to have significantly lower numbers of euploid embryos compared with younger women (P < 0.001). This study found that the SAB rates correlated with blastocyst morphology but were not affected by the maternal age or day of biopsy. The results confirm previous findings that maternal age influences the number of euploid embryos but contraindi-cate the idea that maternal age affects embryo implantation potential.