When should a woman trying to conceive check her Progesterone (PDG) levels?

When to Check PDG (Progesterone) Levels for Women Trying to Conceive

For women trying to conceive, check urine PDG (pregnanediol-3-glucuronide) levels starting 3-4 days after your estimated ovulation or after detecting an LH surge, and continue testing for 3 consecutive days to confirm ovulation occurred. 1

Understanding PDG Testing Timing

Why PDG Timing Matters

• Progesterone rises 24-36 hours after ovulation occurs, making PDG the metabolite that confirms ovulation has already happened, not that it's about to happen 1
• PDG is the major urinary metabolite of progesterone and provides a non-invasive way to confirm ovulation retrospectively 2
• Ovulation typically occurs between cycle days 9-20 in a 28-day cycle, though this varies considerably between women 3, 4

Optimal Testing Window

• Begin PDG testing 3-4 days after your LH surge (the positive ovulation predictor test), as this allows time for ovulation to occur and progesterone to rise 1
• Test for 3 consecutive days to achieve maximum accuracy in confirming ovulation 1
• Studies using ultrasound-confirmed ovulation show that three consecutive tests with a threshold of 5 μg/mL PDG taken after the LH surge confirmed ovulation with 100% specificity 1

Practical Testing Algorithm

Step 1: Identify Your Fertile Window First

• Use LH testing or fertility monitors to detect the LH surge that precedes ovulation by 24-36 hours 5
• Alternatively, track estrogen metabolites (E3G) which rise before ovulation 5

Step 2: Time Your PDG Testing

• Wait 3-4 days after detecting your LH surge before starting PDG testing 1
• This delay is critical because progesterone doesn't rise until after ovulation occurs 1

Step 3: Interpret Results

• A PDG threshold of 5 μg/mL confirmed ovulation in 82% of cycles in women using fertility monitors 1
• Three consecutive positive tests (≥5 μg/mL) provide the highest confidence that ovulation occurred 1
• A 7 μg/mL threshold only confirmed ovulation in 59% of cycles, making it less sensitive 1

Common Pitfalls to Avoid

Timing Errors

• Don't test PDG too early - testing before or immediately after ovulation will give false negatives because progesterone hasn't risen yet 1
• Don't confuse PDG with LH testing - LH predicts ovulation (test before), while PDG confirms it happened (test after) 5, 1

Test Selection Issues

• Automated progesterone immunoassays vary in accuracy - the Abbott Architect platform showed better performance than Roche Cobas for urinary progesterone measurement 2
• PDG ELISA remains the gold standard with a median luteal phase increase of 427% compared to 278% for Abbott Architect and only 146% for Roche Cobas 2

Clinical Context for PDG Testing

When PDG Testing Is Most Useful

• Women with irregular cycles who need confirmation that ovulation actually occurred 1
• Women undergoing ovulation induction where confirming ovulation helps assess treatment efficacy 6, 7
• Women tracking fertility who want retrospective confirmation to time intercourse optimally in future cycles 1

Limitations to Consider

• PDG testing is retrospective - it confirms ovulation already happened but doesn't help time intercourse for the current cycle 1
• 18% of cycles may not show positive PDG even when ovulation occurred, particularly with higher thresholds 1
• PDG levels can be affected by urine concentration, so first morning urine is preferred for consistency 2

Integration with Other Fertility Tracking

Combined Hormone Monitoring

• Modern fertility monitors track E3G, LH, and PDG together to provide a complete picture of the menstrual cycle 5
• E3G and LH help identify the fertile window prospectively, while PDG confirms ovulation retrospectively 5
• This combined approach allows women to optimize timing for the current cycle (using E3G/LH) and confirm success afterward (using PDG) 5, 1