Likelihood of Implantation with Declining E1G After Day 8 Post-LH Peak
Your E1G pattern—rising to 129.9 on day 8 then dropping sharply to 40.2 on day 9 post-LH peak—suggests that implantation and conception remain possible, though the sharp decline in estrogen after the mid-luteal rise is not the typical pattern seen in successful conception cycles.
Understanding Your Hormone Pattern
Your urinary hormone measurements show:
- Day 7 post-LH peak: E1G 43.8
- Day 8 post-LH peak: E1G 129.9 (approximately 3-fold increase)
- Day 9 post-LH peak: E1G 40.2 (sharp drop to baseline)
- PDG: Supplemented at 20 throughout
What These Values Mean
The E1G rise on day 8 is physiologically appropriate. Research demonstrates that urinary estrone-3-glucuronide typically shows a secondary rise during the mid-luteal phase (days 7-9 post-ovulation), reflecting increased estrogen production by the corpus luteum 1, 2. Your peak of 129.9 represents approximately a 3-fold increase from baseline, which falls within the expected 5-7 fold range from early follicular to luteal peak values 1.
However, the sharp decline to 40.2 on day 9 is concerning. In normal ovulatory cycles with adequate luteal function, E1G levels typically remain elevated throughout the mid-luteal phase rather than dropping precipitously after a single day 2, 3. This pattern may indicate:
- Inadequate corpus luteum function despite progesterone supplementation
- A cycle that may not result in pregnancy even if fertilization occurred
- Possible luteal phase deficiency affecting endometrial receptivity
Implantation Timing and Window
Implantation typically occurs 6-12 days after ovulation, with peak implantation at 8-10 days post-ovulation 4. Since you are measuring at days 7-9 post-LH peak (which corresponds roughly to days 6-8 post-ovulation, as ovulation occurs approximately 24-30 hours after LH surge), you are within the critical implantation window 4, 5.
The egg remains viable for only 12-24 hours after ovulation 4, so if fertilization was going to occur, it would have happened by day 1-2 post-ovulation. The question now is whether the endometrial environment can support implantation.
Impact of Progesterone Supplementation
Your PDG supplementation at 20 is artificially maintaining progesterone levels 6, 2. While this supports the endometrial lining structurally, the sharp E1G decline suggests the corpus luteum itself may not be functioning optimally. Research shows that both estrogen and progesterone are required for successful implantation and early pregnancy maintenance 2, 3.
The concern is that supplemented progesterone alone may not compensate for inadequate estrogen production during the critical implantation window. Studies demonstrate that cycles with deficient luteal phases—characterized by inadequate hormone production—have lower implantation rates even when progesterone is supplemented 2.
Clinical Interpretation and Next Steps
Is Pregnancy Still Possible?
Yes, pregnancy remains possible but less likely than in cycles with sustained mid-luteal estrogen elevation. The brief E1G rise on day 8 indicates some corpus luteum activity, and if an embryo is present and healthy, it may still implant despite suboptimal hormonal support 2, 3.
What to Monitor
- Continue progesterone supplementation as prescribed, since stopping now could further compromise any potential pregnancy 6
- Wait until at least 14 days post-ovulation (approximately day 12-13 post-LH peak) before testing for pregnancy 7
- If initial urine pregnancy test is negative at 14 days post-ovulation, repeat testing 2-4 weeks later to definitively exclude pregnancy, as 2-4% of viable pregnancies may still be negative at the typical testing timepoint 7
- Consider serum beta-hCG testing if clinical suspicion remains high despite negative urine tests, as serum tests are more sensitive 7
Common Pitfalls to Avoid
Do not stop progesterone supplementation prematurely based on the E1G decline alone 6. If pregnancy has occurred, abrupt cessation could precipitate pregnancy loss.
Do not rely on a single negative urine pregnancy test to definitively exclude pregnancy 7. Dilute urine, test sensitivity variations, and delayed implantation can all produce false negatives in viable pregnancies.
Do not assume this pattern definitively rules out pregnancy 2, 3. While not optimal, individual variation in hormone patterns means some women may achieve pregnancy despite atypical mid-luteal hormone profiles.
Long-Term Considerations
If this cycle does not result in pregnancy, discuss comprehensive luteal phase evaluation with your fertility specialist 2. The pattern you describe—a brief mid-luteal E1G rise followed by rapid decline—may indicate corpus luteum insufficiency that requires different management strategies in future cycles, such as: