In a 39‑year‑old woman being evaluated after tubal reversal, what day‑3 follicle‑stimulating hormone (FSH) and estradiol (E2) levels are considered normal?

Day 3 FSH and Estradiol Levels in a 39-Year-Old Woman After Tubal Reversal

For a 39-year-old woman being evaluated after tubal reversal, cycle day 3 FSH should be <10 IU/L and estradiol should be <80 pg/mL, with FSH levels >10 IU/L indicating diminished ovarian reserve that may impact fertility outcomes. 1

Normal Reference Ranges for Day 3 Testing

FSH Thresholds

• FSH <10 IU/L indicates normal ovarian reserve and is associated with optimal fertility potential 1
• FSH 10-15 IU/L represents a transitional zone with reduced but not absent fertility potential 2
• FSH >15 IU/L predicts significantly poorer reproductive outcomes, with pregnancy rates dropping substantially 2
• FSH >25 IU/L is associated with very poor prognosis, with ongoing pregnancy rates of only 3.6% per attempt in IVF populations 2

Estradiol Considerations

• Estradiol should be measured concurrently with FSH on day 3 to avoid misinterpretation 1
• Elevated estradiol (>80 pg/mL) on day 3 can artificially suppress FSH through negative feedback, masking diminished ovarian reserve 1
• Normal estradiol during early follicular phase confirms follicular activity and ovarian steroidogenic capacity 1

Critical Testing Parameters

Timing Requirements

• Blood draw must occur specifically on cycle days 3-6, with day 3 being the standard 1, 3
• For women with irregular cycles, timing becomes more challenging and may require alternative markers like anti-Müllerian hormone (AMH) 1
• Testing on day 2 or 4 will yield FSH values within approximately 18% of day 3 values, but estradiol may vary by up to 40% 4

Pre-Test Preparation

• Hormonal contraceptives must be discontinued at least 2 months before testing to allow return of normal pituitary-ovarian axis function 1, 3
• Women should not be on any hormone replacement therapy at time of testing 3

Age-Specific Considerations for This 39-Year-Old Patient

Intercycle Variability

• In women under 40 years, a single day 3 FSH <20 mIU/mL is highly predictive of all subsequent values within a year 4
• However, 15% of women under 40 with initially normal FSH may have an elevated level (≥20 mIU/mL) within the subsequent year 4
• Women aged 40-44 show much greater variability, with 50% of those with initial FSH <20 mIU/mL subsequently showing elevated levels 4

Prognostic Implications at Age 39

• At age 39, this patient is approaching the critical threshold where ovarian reserve declines more rapidly 5
• No pregnancies occurred in women over 40 with day 3 FSH >11.1 mIU/mL in one study examining this age group 5
• Age itself is an independent predictor beyond FSH levels, but FSH provides additional prognostic information 5

Additional Hormonal Assessment

LH Measurement

• LH should be measured concurrently with FSH to calculate the FSH:LH ratio 6
• An FSH:LH ratio >3 predicts poorer follicular development and lower pregnancy rates, even with normal FSH levels 6
• LH:FSH ratio >2 suggests polycystic ovary syndrome (PCOS) and likely anovulation 1
• Low LH (<3 mIU/mL) may indicate a trend toward poorer reproductive outcomes 6

Confirmation of Ovulation

• Normal baseline FSH and estradiol do not guarantee ovulation 1
• Mid-luteal progesterone (approximately cycle day 21) should be measured to confirm ovulation, with levels ≥6 nmol/L indicating ovulation occurred 1

Common Pitfalls to Avoid

Interpretation Errors

• Do not rely on a single elevated FSH if estradiol is also elevated (>80 pg/mL), as the elevated estradiol may have suppressed FSH in previous cycles 1
• Patients with large intercycle FSH variation respond poorly to stimulation independent of their mean FSH concentration 7
• Regular menstrual cycles do not guarantee normal ovarian reserve in women approaching 40 3

Testing Conditions

• Measurements during hormonal contraceptive use will mask underlying abnormalities 3
• Failing to measure both FSH and estradiol together can lead to false reassurance 1
• Testing outside the day 3-6 window reduces accuracy and comparability to established thresholds 1, 3

When to Pursue Further Evaluation

Additional testing is warranted if:

• FSH is 10-15 IU/L (borderline diminished reserve) 1, 2
• Estradiol is elevated (>80 pg/mL) on day 3 1
• FSH:LH ratio is >3 6
• Patient has menstrual irregularities despite normal hormone levels 1
• Infertility persists after 6 months of attempting conception (given age >35) 3

Consider AMH testing as it does not vary by menstrual day and provides additional information about ovarian reserve 1, 3