E1G Levels and Implantation: What to Expect
I cannot predict your E1G level tomorrow based on the pattern you've described, because E1G (estrone-3-glucuronide) does not reliably change in response to implantation in a way that can be predicted from pre-implantation values 1, 2.
Why E1G Cannot Predict Implantation
E1G is a marker of ovarian follicular activity and estrogen production, not a marker of implantation. The hormone primarily reflects what your ovaries are doing—specifically, follicle development before ovulation and corpus luteum function after ovulation 1, 3, 4.
The Pattern You're Describing
Your E1G pattern shows:
- Day 7 post-LH peak: 43.8 nmol/L
- Day 8 post-LH peak: 129.9 nmol/L (a 3-fold rise)
- Day 9 post-LH peak: 40.2 nmol/L (dropped back down)
This fluctuation is actually within the range of normal luteal phase variation that occurs in healthy ovulatory cycles, independent of whether implantation occurs 2. Studies show that 77% of normal ovulatory cycles differ from "mean curve patterns," with fluctuations, double peaks, and pre/post-peak surges being common 2.
What Happens at Implantation
Implantation (which typically occurs 6-12 days post-ovulation, or roughly 5-11 days post-LH peak) triggers hCG production by the developing embryo, not a predictable change in E1G 5, 6. The hCG then supports the corpus luteum to continue progesterone production, but E1G patterns during this window are highly variable and not diagnostic 1, 2.
The Hormone That Actually Indicates Implantation
If implantation has occurred, you should measure serum β-hCG (not E1G) starting around 9-11 days post-ovulation (roughly 8-10 days post-LH peak) 5, 6.
- hCG becomes detectable in serum approximately 9 days after conception 5.
- Urine pregnancy tests (detecting hCG at 20-25 mIU/mL) typically become positive 11 days past expected menses, which corresponds to roughly 11-14 days post-ovulation 5.
- Serial hCG measurements 48 hours apart are far more useful than single values for confirming viable early pregnancy 6.
Expected hCG Pattern if Implantation Occurred
If implantation happened around days 6-9 post-LH peak:
- Initial hCG rise begins within 24-48 hours of implantation 5.
- hCG doubles approximately every 48-72 hours in viable early pregnancy 6.
- By 10-12 days post-LH peak, serum hCG should be detectable (>5 mIU/mL) if implantation was successful 5, 6.
What Your E1G Pattern Actually Tells You
Your E1G fluctuation (43.8 → 129.9 → 40.2) most likely reflects normal luteal phase ovarian activity, not implantation status 1, 2. The rise and fall you observed is consistent with:
- Secondary estrogen surges during the luteal phase, which occur in many normal cycles 2.
- Day-to-day variability in steroid hormone excretion, which is common even in fertile cycles 2.
- Corpus luteum function fluctuations, which produce variable E1G levels throughout the luteal phase 1, 4.
The Ratio That Matters More
The ratio of E1G to pregnanediol-3α-glucuronide (PdG) is more informative than E1G alone for assessing luteal phase adequacy 1, 4, 7. A declining E1G/PdG ratio after ovulation indicates adequate progesterone production, which is necessary (but not sufficient) for implantation 1, 4.
Bottom Line
Stop monitoring E1G to detect implantation—it won't work. Instead:
- Wait until at least 10-12 days post-LH peak (or first day of missed period) 5.
- Obtain a serum quantitative β-hCG test if you want the earliest possible detection 5, 6.
- Repeat the hCG measurement 48 hours later to confirm appropriate doubling (≥53% rise) if the first value is positive but low 6.
- Use a sensitive urine pregnancy test (detecting 20-25 mIU/mL) starting 11-14 days post-ovulation for home testing 5.
E1G tomorrow will reflect your ovarian activity, not implantation status, and could be anywhere from 20-150 nmol/L based on normal luteal phase variability 2, 4.