Background ,Pregnanediol glucuronide (PdG), the principal urinary metabolite of progesterone, can assess luteal progesterone exposure, but interpretation depends on appropriate timing relative to ovulation. We evaluated whether urinary luteinizing hormone (LH)-based reference points could standardize luteal urinary PdG assessment compared with ultrasound-determined ovulation (USDO).,Methods,This retrospective secondary analysis included 216 ovulatory cycles from 95 women from an original cohort of 107 women (326 cycles). Eligible cycles had ultrasound-confirmed ovulation and an LH peak before USDO+3. The retrospectively identified LH peak and first urinary LH concentrations ≥10, ≥15, ≥20, ≥25, and ≥30 mIU/mL were evaluated for timing urinary PdG measurement 6–9 days later, using a prespecified threshold of ≥15 µg/mL. PdG classifications were compared with USDO-timed classifications using area under the receiver operating characteristic curve, sensitivity, specificity, predictive values, and likelihood ratios.,Results,Agreement remained high across assessment days. The LH peak showed the highest overall agreement. Among prospectively applicable strategies, first urinary LH ≥15 mIU/mL provided the best balance between agreement and cycle availability. Positive predictive values were consistently high (98–100%), whereas negative predictive values were modest. No assessment day consistently outperformed the others.,Conclusions,Urinary LH-based timing closely reproduced USDO-guided urinary PdG classification. The LH peak showed the highest agreement, whereas first urinary LH ≥15 mIU/mL was the most practical prospective reference point. PdG ≥15 µg/mL classifications showed near-universal agreement with ultrasound-guided timing. These findings support standardized PdG timing when ultrasound is unavailable but do not establish diagnostic criteria or predict reproductive outcomes.
