Post-wash total progressively motile sperm count thresholds and clinical pregnancy after intrauterine insemination: a systematic review and meta-analysis

The prognostic value of the post-wash total progressively motile sperm count (TPMSC) for intrauterine insemination (IUI) remains debated, with heterogeneous thresholds reported. To quantify the association between post-wash TPMSC and clinical pregnancy after IUI across commonly used thresholds (1 × 106, 5 × 106, and 10 × 106 motile sperm) and to examine for a plateau effect beyond 10 × 106. We performed a PRISMA-guided systematic review and meta-analysis of observational studies (PROSPERO registration pending). Two reviewers independently screened, extracted data, and appraised study quality using the Newcastle–Ottawa Scale (NOS; max 9). The primary outcome was clinical pregnancy rate (CPR), generally defined as an ultrasound-confirmed intrauterine gestational sac. Random-effects (DerSimonian–Laird) models generated pooled odds ratios (ORs) with 95% confidence intervals (CIs). Heterogeneity was assessed with I2 and Cochran’s Q. Sensitivity analyses were prespecified but not performed. Nine retrospective cohort studies encompassing 110,723 IUI cycles from 44,438 couples published between 2002 and 2023 were included in the quantitative synthesis. Higher post-wash TPMSC was consistently associated with increased clinical pregnancy rates across all thresholds, although the magnitude of benefit decreased with higher sperm counts. Compared with ≤1 × 106, cycles with TPMSC > 1 × 106 had more than twice the odds of achieving clinical pregnancy (OR 2.30, 95% CI 1.38–3.85; I2 = 79.4%). At the 5 × 106 cutoff, the association remained significant (OR 1.73, 95% CI 1.42–2.10; I2 = 74.2%), and at the 10 × 106 threshold, the effect persisted but was attenuated (OR 1.41, 95% CI 1.27–1.55; I2 = 62.2%). In a direct comparison between intermediate (5–10 × 106) and higher (>10 × 106) TPMSC categories, a modest yet statistically significant advantage was observed for the latter (OR 1.17, 95% CI 1.04–1.32; I2 = 54.6%), indicating a plateau in clinical benefit beyond approximately 10 × 106 motile sperm. Post-wash TPMSC is a meaningful predictor of IUI clinical pregnancy, with the largest relative gain above 1 × 106, clinically relevant improvement up to 5 × 106, and diminishing returns beyond ~10 × 106. These data support a tiered counseling framework in which TPMSC informs—without solely determining—treatment selection and timing of transition to in vitro fertilization/intracytoplasmic sperm injection.