Embryological perspectives on biochemical pregnancy and early miscarriage risks: a retrospective cohort study

Do chromosomal constitution, developmental speed, and morphological grading correlate with biochemical pregnancy, early miscarriage, and overall pregnancy loss?

This study retrospectively analyzed a total of 12,527 frozen single blastocyst transfer cycles conducted between January 2022 and December 2023. All enrolled subjects were divided into a preimplantation genetic testing (PGT) group (2,104 cycles) and a non-PGT group (10,423 cycles).

Transfer of day 5 blastocysts significantly reduced the rates of biochemical pregnancy and early miscarriage compared with day 6 blastocysts. In non-genetically tested cycles, biochemical pregnancy rates were 8.4 % (day 5) vs 16.5 % (day 6, p < 0.001), and early miscarriage rates were 15.8 % vs 24.5 % (p < 0.001). In genetically tested cycles, these rates were 7.6 % (day 5) vs 16.8 % (day 6, p < 0.001) and 8.3 % vs 19.1 % (p < 0.001), respectively. The adjusted odds ratios (aORs) were 0.48 (95 % CI: 0.40-0.58) for biochemical pregnancy, 0.65 (95 % CI: 0.57-0.75) for early miscarriage, and 0.51 (95 % CI: 0.45-0.58) for the overall pregnancy loss rate. Euploid blastocysts showed a significant reduction in early miscarriage rates compared with non-genetically tested blastocysts (aOR = 0.75, 95 % CI: 0.59-0.95). However, blastocyst morphological grading was not significantly associated with biochemical pregnancy or early miscarriage.

Blastocyst developmental speed serves as the strongest predictor for biochemical pregnancy and early pregnancy loss, and preimplantation genetic testing is associated with reduced risk of early miscarriage.