Often called the “hormone of pregnancy”, progesterone plays a much bigger role in the menstrual cycle than you might realise. Here’s what every woman should know about this important hormone, from ovulation to implantation and beyond.
When it comes to reproductive health, oestrogen tends to get most of the attention. But quietly working alongside it is progesterone – a hormone that plays an essential role in preparing the body for pregnancy and supporting the earliest stages of it.
Whether you’re actively trying to conceive, simply learning more about your cycle or wondering what your hormones are actually doing each month, understanding progesterone can offer useful insight into how your reproductive system works.
So, what exactly is progesterone?
Progesterone is a steroid hormone produced primarily by the corpus luteum – a temporary structure that forms in the ovary after ovulation.
Its levels are relatively low during the first half of the menstrual cycle. After ovulation, however, progesterone rises during what is known as the luteal phase.
This rise isn’t accidental. Progesterone helps transform the lining of the uterus into an environment that can support a fertilised egg.
If pregnancy doesn’t occur, progesterone levels eventually fall. This hormonal drop contributes to the shedding of the uterine lining, otherwise known as your period and the cycle begins again.
What does progesterone have to do with ovulation?
Progesterone is primarily a post-ovulation hormone, rather than the hormone that triggers ovulation itself.
Ovulation is largely driven by a surge in luteinising hormone (LH). Once an egg has been released, the corpus luteum produces progesterone.
This makes progesterone particularly useful when looking at whether ovulation has occurred. A progesterone blood test performed at the appropriate point in the cycle can provide evidence of recent ovulation.
The timing matters, though. Progesterone fluctuates significantly throughout the luteal phase, so a single result needs to be interpreted in the context of the menstrual cycle and the individual.
Progesterone’s role in fertility
Think of ovulation as releasing the egg and progesterone as helping prepare the room for a potential guest.
After ovulation, progesterone helps:
Prepare the uterine lining: It encourages the endometrium to become receptive to a fertilised egg.
Support implantation: A suitably prepared uterine lining is important for an embryo to implant successfully.
Support early pregnancy: If conception occurs, progesterone remains important in maintaining the uterine environment during early pregnancy. Eventually, the placenta becomes the major source of progesterone.
Regulate the menstrual cycle: The rise and subsequent fall of progesterone help coordinate the second half of the menstrual cycle and the onset of menstruation.
So while progesterone isn’t responsible for making you ovulate, it is an important part of what happens after ovulation.
What happens to progesterone if you become pregnant?
If an egg is fertilised and implantation occurs, hormonal signals help maintain the corpus luteum, allowing it to continue producing progesterone.
Progesterone helps maintain the uterine lining and supports the environment needed for pregnancy.
As pregnancy progresses, the placenta takes over progesterone production. Levels remain considerably higher throughout pregnancy than they are during a typical menstrual cycle.
What does “low progesterone” actually mean?
You may have heard the term “low progesterone” online, particularly in conversations around fertility. But interpreting progesterone isn’t quite as simple as looking at one number.
Progesterone naturally changes throughout the menstrual cycle, and the level considered appropriate depends on when the test was taken.
A low result at one point in the cycle may be completely different from a low result after ovulation.
Doctors may investigate progesterone when there are concerns about ovulation, irregular menstrual cycles, infertility or recurrent pregnancy loss. However, progesterone is only one piece of the fertility picture.
Can progesterone affect your period?
Yes. Progesterone is closely involved in the menstrual cycle.
After ovulation, progesterone rises. If pregnancy doesn’t occur, the corpus luteum breaks down and progesterone falls. This hormonal withdrawal contributes to the breakdown and shedding of the uterine lining.
Changes in progesterone and the balance between reproductive hormones can also be associated with symptoms such as breast tenderness, bloating and mood changes during the luteal phase.
Progesterone and PMS: is there a connection?
The luteal phase is when many women experience premenstrual symptoms, and this is also when progesterone is elevated.
But PMS isn’t simply caused by having “too much” or “too little” progesterone. The picture is more complicated and involves hormonal fluctuations and individual sensitivity to those changes.
This is one reason why diagnosing yourself based on symptoms – or assuming every PMS symptom means you have a progesterone problem – can be misleading.
Can you naturally increase progesterone?
This is where fertility advice online can become confusing.
You may see claims that particular foods, supplements or lifestyle hacks can dramatically increase progesterone. There isn’t strong evidence that a specific food can reliably raise progesterone enough to correct a clinically significant hormonal problem.
Instead, supporting overall reproductive health means focusing on the foundations: adequate nutrition, sufficient energy intake, regular movement, good-quality sleep and managing excessive physical or psychological stress.
If ovulation isn’t occurring regularly, addressing the underlying reason is more useful than simply trying to increase progesterone.
And importantly, don’t start progesterone supplements or hormonal treatments without medical guidance.
What about progesterone supplements?
Progesterone is available in prescription forms and is used in a number of reproductive-health situations.
For example, progesterone may be prescribed as part of some fertility treatments or after certain assisted reproductive procedures. It may also have specific uses during pregnancy for some women.
However, progesterone isn’t a universal fertility treatment. Whether supplementation is appropriate depends on the individual’s circumstances, medical history and the reason for treatment.
Can progesterone tell you if you are fertile?
Not on its own.
A progesterone test can help provide information about whether ovulation has occurred, but fertility is influenced by considerably more than one hormone.
Age, ovarian reserve, ovulation, fallopian-tube health, uterine factors, sperm health and other hormonal and medical factors can all influence the ability to conceive.
Think of progesterone as one clue in a much bigger fertility picture, rather than a fertility score.
Progesterone might not be the hormone you hear about most often, but its role in reproductive health is significant. Rising after ovulation, it helps prepare the uterine lining, supports implantation and plays an important role in maintaining early pregnancy.
The most important thing to remember is that hormones aren’t isolated switches. They work together, change throughout the menstrual cycle and need to be interpreted in context.
If you’re experiencing irregular periods, difficulty conceiving, repeated pregnancy loss or other concerns about your cycle, speaking to a GP, gynaecologist or fertility specialist is a better starting point than trying to diagnose a hormone imbalance from symptoms or an at-home test.
Because understanding your hormones isn’t about chasing “perfect” levels – it’s about understanding what your body is doing and getting the right information when something doesn’t feel right.
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