Ovulation occurs when a mature egg is released from the ovary into the fallopian tube, where it can be fertilized by sperm. The egg survives 12–24 hours; sperm can survive up to 5 days.
Fertile Window
The fertile window spans about 6 days: 5 days before ovulation + the day of ovulation itself. This is when conception is most likely.
Signs of Ovulation
- Rise in basal body temperature (0.5–1°F)
- Change in cervical mucus (clear, slippery, egg-white consistency)
- Mild pelvic pain (mittelschmerz)
- Positive ovulation predictor kit (OPK) — detects LH surge
Ovulation Predictor Kits vs. Basal Body Temperature
OPKs detect the LH surge that precedes ovulation by 24–36 hours, making them predictive — useful for timing intercourse in advance. Basal body temperature only confirms ovulation has already happened (temperature rises after the fact), making it more useful for confirming a pattern over several cycles than for real-time prediction.
Cycle Irregularity
Ovulation doesn't always occur exactly on day 14 — cycle length and ovulation timing vary between individuals and even cycle to cycle for the same person, influenced by stress, illness, and conditions like PCOS. Tracking several cycles gives a far more accurate personal fertile window than assuming a textbook 28-day cycle.