Did I ovulate on cycle day 13‑14, and when should I start progesterone for luteal‑phase insufficiency; is the egg still viable for fertilization on late day 15 or day 16 after I began progesterone at 1 pm on day 15?

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Ovulation Timing and Progesterone Supplementation

Based on your hormone pattern, you ovulated on cycle day 13-14, the egg was likely no longer viable by late cycle day 15 when you started progesterone, but continuing progesterone through at least cycle day 20-21 is appropriate given your documented luteal insufficiency. 1

When Did Ovulation Occur?

Your LH surge peaked at 45 IU/L on cycle day 13, which predicts ovulation occurred within 24-36 hours of that peak—meaning ovulation most likely happened between late cycle day 13 and early cycle day 14. 1 The rise in your PDG from 3.1 on cycle day 13 to 4.7 on cycle day 14 confirms corpus luteum formation after follicular rupture, providing biochemical evidence that ovulation occurred during this window. 1

The intense pelvic pressure you experienced on cycle day 14 at 5:50 PM is consistent with the timing of follicular rupture and ovulation. 1

Egg Viability Window

The oocyte remains viable for only 12-24 hours after ovulation. 1 Since ovulation occurred on cycle day 13-14, the egg's viable window closed by late cycle day 14 or early cycle day 15. 1

  • Intercourse occurring 24-48 hours after ovulation falls at the outer limit or beyond the egg's viable window, substantially reducing the likelihood of conception. 1
  • By the time you had intercourse and started progesterone at 1 PM on cycle day 15, you were approximately 24-36 hours post-ovulation, which is at or beyond the egg's fertilization window. 1

Evidence of Luteal Phase Insufficiency

Your progesterone pattern demonstrates clear luteal insufficiency requiring supplementation. The critical finding is that your PDG dropped to 2.1 on cycle day 15—below your baseline of 3.2 from cycle day 5. 1 This decline within two days of the LH surge is considered definitive evidence of inadequate corpus luteum function. 1

According to the American College of Obstetricians and Gynecologists, progesterone concentrations below 6 nmol/L (approximately <2 ng/mL) indicate inadequate luteal function. 1 Mid-luteal progesterone should be ≥5 ng/mL; values below this threshold denote luteal insufficiency and require supplementation. 1, 2

Timing of Progesterone Supplementation

You started progesterone at the appropriate time. Initiating progesterone on the afternoon of cycle day 15 was correct because the observed progesterone decline indicated luteal insufficiency. 1 A drop in progesterone within two days of the LH surge warrants immediate luteal-phase support. 1

Does Progesterone Affect Fertilization?

Exogenous progesterone does not impede sperm from reaching or fertilizing a still-viable oocyte. 1 However, given that you started progesterone approximately 24-36 hours post-ovulation, the egg was likely at the very end of or beyond its viable window regardless of progesterone administration. 1

Current Status and Next Steps

Continue progesterone supplementation for at least 7 days after ovulation (through approximately cycle day 20-21) to support potential implantation. 1 The cramping you experienced on cycle day 15 likely represents post-ovulatory changes rather than ongoing ovulation, as ovulation was completed by cycle day 14. 1

Important Caveats

  • Exogenous progesterone supplementation will artificially elevate your progesterone levels, which may complicate interpretation of endogenous hormone trends going forward. 1, 2
  • If menstruation does not occur by your expected date, perform a serum β-hCG test to definitively confirm or exclude pregnancy. 1
  • If β-hCG is negative but uncertainty remains, repeat testing in 3-4 days, as hCG doubles approximately every 48 hours in viable early pregnancy. 2

Clinical Reality

While the timing of intercourse on cycle day 15 was likely beyond the optimal fertile window (which extends from 5 days before ovulation through 24 hours after), 3 conception remains theoretically possible if ovulation occurred at the later end of the predicted window. 1 The progesterone supplementation you initiated is appropriate for your documented luteal insufficiency and will not interfere with any potential fertilization that may have occurred. 1

References

1
Guideline

Guideline Summary: Ovidence of Ovulation, Lute‑Phase Insufficiency, and Progester‑One Therapy

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

2
Guideline

Interpretation of Hormone Patterns in Luteal Phase

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

3
Research

Accuracy of perception of ovulation day in women trying to conceive.

Current medical research and opinion, 2012

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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