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Ovulation typically occurs 14 days before the next period. For a 28-day cycle, add 14 days to LMP to estimate ovulation/conception. Fertilization occurs within 12–24 hours of ovulation; sperm can survive 3–5 days. Cycle length variability means conception windows shift—this is an estimate, not a clinical determination. Confirm dates with an OB/GYN.
Rough estimate: conception ~14 days after LMP start.
1/15/2026