Trigger-day progesterone-to-mature-oocyte ratio, cycle-level blastocyst yield, and recorded embryo-transfer outcomes: a retrospective cohort study

Background The progesterone-to-metaphase II oocyte ratio (P/MII) combines trigger-day progesterone with mature oocyte count after retrieval. Its associations may reflect ovarian response and embryo allocation. Methods This retrospective cohort included 7,778 in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycle records. Existing pregnancy analyses used 4,273 positive-transfer records. A linked clinical and laboratory source export enabled post hoc analyses using recorded extended culture counts, retrieval order, transfer dates, thawing records, and source-identifier grouping. Results The original high-versus-low P/MII rate ratio for blastocysts per recorded 2PN zygote was 0.796 (95% CI 0.762–0.831). Among the same 5,821 culture-positive records, the adjusted rate ratio was 0.934 (0.902–0.968) with a 2PN denominator and 0.974 (0.945–1.005; P = 0.101) with the recorded culture denominator. The continuous culture-count association remained small (aRR 0.993 per 0.01, 0.989–0.997). The source recorded 6,148 first and 1,630 later retrievals. In 3,526 first-retrieval, date-consistent records without thawing evidence, the ratio term after inclusion of progesterone and MII was associated with clinical pregnancy flags (aOR 0.952, 0.919–0.986; P = 0.006) but was uncertain for live birth flags (0.968, 0.935–1.002; P = 0.067). Source-identifier-grouped live birth areas under the receiver operating characteristic curve (AUCs) were 0.623 with the components, 0.623 with P/MII, and 0.624 with all three. Conclusions Recorded associations depended on the culture population, denominator, and outcome. Incremental clinical usefulness was not established. These data do not support a physiological ratio mechanism or a clinical cutoff for trigger-day or freeze-all decisions.