Comparison of Pregnancy Outcomes from Fresh Transfer of High-Quality Single Blastocysts in Women of Different Ages: A Retrospective Study.

ObjectiveTo compare pregnancy and neonatal outcomes following fresh high-quality single blastocyst transfer (SBT) across different maternal age groups.MethodsThis retrospective cohort study included 4352 women who underwent fresh high-quality SBT and were divided into three age groups: <30 years (Group A, n = 1939), 30-34 years (Group B, n = 1801), and 35-37 years (Group C, n = 612). Baseline characteristics, pregnancy outcomes, and neonatal outcomes were compared across the groups. Non-live birth was the prespecified primary outcome. For secondary and exploratory outcomes, P values were adjusted for multiple comparisons using the Bonferroni method.ResultsWomen in Group A had a significantly higher live birth rate than those in Group C (56.88% vs 43.79%; P < 0.001). No significant differences were observed between Groups A and B. The miscarriage rate in Group C (20.94%) was significantly higher than that in Group A (11.48%; P < 0.001); however, the difference compared with Group B (14.06%) did not remain significant after Bonferroni correction. Exploratory differences in preterm birth, gestational diabetes mellitus, and birth defects were also not statistically significant after correction. Multivariable analysis showed that maternal age 35-37 years was independently associated with higher odds of non-live birth (OR = 1.539, 95% CI 1.220-1.942) and adverse pregnancy outcomes (OR = 1.515, 95% CI 1.135-2.024), whereas age 30-34 years was not.ConclusionsAmong women undergoing fresh high-quality SBT, those aged 30-34 years achieved pregnancy outcomes comparable to those of women aged <30 years, whereas women aged 35-37 years had significantly lower live birth rates and higher miscarriage rates. These findings reflect age-related differences within the SBT population rather than a comparison between transfer strategies. Large-scale prospective multicenter randomized trials are warranted.