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The fertility window is the 6-day period when conception is possible — 5 days before ovulation and ovulation day itself. Ovulation typically occurs 14 days before the next period.

Formula

Ovulation typically day 14 of 28-day cycle (range 12–16). Fertile window: day 12–16 (5 days pre-ovulation, day of ovulation). Sperm viable 5 days; egg 12–24 hours.
CycleLength
Menstrual cycle length (Days (typical 28, range 21–35))
OvulationDay
Expected ovulation (Days from cycle start)
FertileWindow
Peak fertility window (Days (5–6 day window))

Guida passo passo

  1. 1Ovulation ≈ Cycle length − 14 days from LMP
  2. 2Fertile window = Ovulation − 5 days to Ovulation day
  3. 3Sperm survive 3–5 days; egg survives ~12–24 hours
  4. 4OPK tests and basal body temperature confirm ovulation

Esempi risolti

Ingresso
30-day cycle, LMP 1 January
Risultato
Ovulation ≈ Jan 16; Fertile window: Jan 11–16

Domande frequenti

How do I predict ovulation?

Calendar method: ovulation = cycle length − 14 days (average). LH surge kits detect surge 24–36 hrs before ovulation (most accurate). Basal body temperature rise (0.5°C) confirms ovulation post-hoc.

Does cycle length variation matter?

Yes. 28-day cycles: simple prediction. 21–35 days normal but unpredictable. Track 3 months minimum to establish pattern. Apps (Clue, Flo) help predict best.

What decreases conception chances?

Irregular cycles, anovulation (no ovulation), poor egg/sperm quality, timing (intercourse every 2–3 days throughout cycle > precise timing), age (female fertility drops 35+).

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