Progesterone
A hormone produced mainly by the corpus luteum after ovulation that prepares the uterus for a possible pregnancy and shapes the second half of the menstrual cycle.
Progesterone defines the luteal phase, raises basal body temperature, and dries up fertile cervical mucus, all of which fertility awareness methods use as indirect signs that ovulation has occurred.
Progesterone is one of the two main reproductive hormones in the menstrual cycle, working together with estrogen. Levels rise sharply after ovulation, when the corpus luteum begins producing it, and stay elevated for the rest of the cycle. If pregnancy occurs, progesterone continues to rise; if it does not, levels fall and a period follows.
Why it matters for fertility awareness
Progesterone is the reason basal body temperature rises after ovulation. It is also why cervical mucus changes from fertile-type to dry or sticky. These two changes give a person who is charting a clear signal that the body has shifted from the follicular phase into the luteal phase.
How it relates to NFP
Most NFP methods do not measure progesterone directly. Instead, they read its effects: a sustained temperature shift over several days, a closing-up of the fertile mucus pattern, and, in monitor-based methods, the disappearance of the LH surge. Together, these signs suggest the luteal phase has begun.
What it does not mean
- Basal body temperature does not measure progesterone directly; it reflects the effect of progesterone on the body.
- A normal temperature shift does not prove that progesterone levels are clinically adequate.
- Concerns about a short luteal phase, low progesterone, or recurrent miscarriage should be evaluated by a clinician.
Related terms
- Luteal phase, /glossary/luteal-phase
- Corpus luteum, /glossary/corpus-luteum
- Basal body temperature, /glossary/basal-body-temperature
- Estrogen, /glossary/estrogen
- Ovulation, /glossary/ovulation
Related reading
- The science of cycle tracking, /guides/science-of-cycle-tracking
- Can NFP help you get pregnant, /questions/can-nfp-help-you-get-pregnant