The Human Reproductive System
Cycle phaseovulation
Fertile windowYes
Oestrogen97
Progesterone5
Uterine lining6.0 mm
- Move to day 1 — confirm the cycle is in its menstrual phase with the lining at its thinnest
- Move to day 14 — confirm ovulation is occurring
- Find a day within the fertile window, a few days before ovulation
- Move to day 21 — confirm progesterone is now higher than oestrogen
- Find the day where the uterine lining is at its thickest, in the luteal phase