Guest post by Dr. Lakshmi Vaswani from Inito Fertility Monitor

If you’re a woman trying to optimize your metabolism, improve your hormonal health, and support your fertility- especially if you’re trying to conceive- progesterone should be on your radar.

Although it’s known as the ‘pregnancy hormone’, progesterone actually plays key roles not only during but also before and after pregnancy. It’s one of the main female sex hormones along with estrogen, and the two must exist in a specific balance for optimal health!

And unfortunately, many providers in the conventional healthcare space don’t emphasize its importance enough.You may have had your progesterone levels checked if your doctor ever ran a hormone panel (or you specifically asked for one). And of course, those who go through Assisted Reproductive Technology (ART) procedures, such as in-vitro fertilization (IVF), have their levels checked regularly throughout the process to ensure the pregnancy progresses smoothly.

But otherwise, it seems that more attention needs to be paid to this absolutely crucial hormone! In a perfect world, more doctors would stress on its importance for your health and especially your pregnancy journey because it's kind of a big deal!

The bottom line is- healthy progesterone levels are essential for women, especially those who want to become pregnant. Read on to discover how progesterone affects fertility, pregnancy, and overall health, and how you know if you’re producing enough.

Disclosure: This post contains affiliate links, meaning I get a commission if you decide to make a purchase through my links, at no cost to you.

Let’s dive into progesterone! What is it, and how is it produced?

Chemically, progesterone is a steroid hormone normally produced naturally by the body (in the ovaries and a small amount in the adrenal glands as well as by the placenta during pregnancy. Men do produce small progesterone levels in their testes. However, for women, this hormone plays much more impactful roles and levels fluctuate normally throughout the menstrual cycle. (Natural progesterone is also very different from progestin, which is the synthetic form found in hormonal birth control).

During each cycle, a mature follicle in your ovary releases an egg (this is called ovulation) and leaves behind the broken follicle (called the corpus luteum), which then begins secreting progesterone. Levels increase, peaking around 5-9 days post-ovulation. In fact, without ovulation each cycle, it’s impossible to produce sufficient levels of this important hormone!

If male sperm fertilizes this egg, it forms an embryo that implants itself into the thick inner lining of the uterus to grow into a fetus. Then, the placenta is formed to provide the baby with oxygen and nutrients at around the 10th week of pregnancy. The placenta then takes over progesterone production until delivery.

If the egg is not fertilized, implantation does not occur, the placenta is not formed, and the corpus luteum degenerates. With this, your progesterone levels will suddenly drop, and the thickened uterine lining sheds when you experience menstrual bleeding, marking the start of another monthly cycle.

Progesterone carries out essential functions before and during pregnancy but also throughout life.

Here are 6 reasons to ensure your progesterone levels are optimal:

1. Supporting a healthy metabolism: progesterone is involved in energy production and use.

Progesterone supports the metabolism, therefore helping the body more effectively produce, regulate, and utilize energy.

For one, it’s crucial for proper functioning of the thyroid. Low levels of progesterone can increase Thyroid Binding Globulin (TBG), inhibiting the amount of thyroid hormone available for use in the body.

Progesterone- particularly in a healthy balance with estrogen- is also important for maintaining insulin levels for proper blood sugar handling.

2. Improving mood and mental health: progesterone is a very relaxing hormone.

Progesterone is a naturally calming and soothing hormone for both the body and the mind. In fact, it’s classified as a neurosteroid, meaning it stimulates normal brain processes and supports the functioning of the nervous system!

This amazing hormone directly supports mood and mental health, easing anxiety, increasing stress resilience, and supporting sleep.

Producing sufficient progesterone also prevents intense PMS symptoms, including mood swings, insomnia, and anxiety.

3. Marking ovulation: increased progesterone levels confirms ovulation and therefore, fertility.

Knowing if and when you ovulate is important because it means you’re fertile! But there’s a common misconception that pinpointing ovulation is only helpful when you are trying to conceive. However, it’s also when you’re trying to prevent pregnancy (so you know when to abstain or use a barrier method for protection).

Either way, ovulating regularly is crucial for overall health to ensure you’re making progesterone.

Through your follicular phase and before ovulation, your progesterone levels remain fairly low. Then, your body releases luteinizing hormone (LH) with a sudden surge, which causes the follicle to rupture, releasing the egg for fertilization. The corpus luteum then releases progesterone, leading to this spike in progesterone levels.

There are a few ways women aim to pinpoint ovulation that aren’t necessarily accurate. One common way is just using a period tracking app that estimates ovulation around half-way through the cycle, which isn’t the case for all women.

Another way is using ovulation-predictor kits (OPKs) which detect the LH surge that occurs prior to ovulation. However, it is possible to have an LH surge and not ovulate. Some women also feel mild symptoms around ovulation, but these can be for other reasons and again, cannot confirm ovulation.

The only way to confirm ovulation is a rise in progesterone levels.

And PS: If you’re on hormonal birth control, you do not ovulate and actually don’t have your own cycle. The bleed you experience is a hormone withdrawal-induced bleed and not a true period.

4. Maintaining strong bones: progesterone helps prevent osteoporosis.

Progesterone promotes bone building by stimulating osteoblasts (cells that make new bone). It plays an important role in preventing osteoporosis- before but especially after menopause.

Low estrogen during menopause is believed to cause osteoporosis, but progesterone’s role in bone health is often overlooked.

This is one reason why regular ovulatory cycles in your menstruating years are important. Each monthly(ish) “deposit” of this hormone building the bank account that you’ll utilize post-menopause, when hormone production decreases dramatically.

To achieve a healthy bone mass now and enjoy the benefits of strong, healthy bones through life, you must ensure that your progesterone and estrogen hormone levels are well balanced. (And also strength train, too!)

5. Building the baby bump: Progesterone helps the uterus prepare for pregnancy and supports fetal growth.

Progesterone prepares the endometrium (lining of the uterus) for implantation, thickening it so that a fertilized egg can be securely attached. Progesterone also acts as a smooth muscle relaxant that decreases contractions in the uterine wall so that the fertilized egg is not dislodged after implantation.

The importance of progesterone then continues throughout pregnancy. Increased levels:

Nurture the fetus as it grows
Prevents ovulation from occurring again
Prevents contractions that may result in preterm labor
Help the mother’s immune system tolerate the “foreign” DNA
Help the breast tissue to develop
Prepare the breasts and mammary glands for milk production and breastfeeding

Therefore, a low progesterone level can be a cause of infertility. It can also lead to ectopic pregnancy, where the fertilized egg implants itself outside the uterus, which could be life-threatening without immediate medical care.

6. Protecting new life: Progesterone helps prevent miscarriages.

A miscarriage can be a devastating and even traumatic loss, especially for women dealing with infertility and/or experiencing recurrent loss.. Losing a baby inside the womb is physically and emotionally draining for a woman and her family.

Unfortunately, miscarriages are fairly common, with 10 to 15 pregnancies out of 100 ending in miscarriage. 1% of women even have repeat miscarriages.

Some miscarriages are spontaneous, and we don’t know what the cause could be. However, studies show that during normal pregnancy in the first trimester, progesterone levels should value above 25 ng/mL about 98% of the time. Since progesterone is necessary for a healthy pregnancy, low levels of progesterone could increase the chances of miscarriage.

In fact, supplemental forms of progesterone have been broadly used in reproductive medicine as a strategy for miscarriage prevention after recurrent losses and also for prevention of preterm birth. This can of course be life-saving but why not focus more on adequate production of progesterone before pregnancy more?

Could your progesterone be low?

There are ways to measure progesterone, but like so many other things, we can begin by listening to our bodies. They communicate with us through different signs and symptoms.

Low progesterone levels can cause symptoms like:

Anxiety
Mood swings
Weight gain
Abnormal uterine bleeding or irregular periods
Too short or long menstrual cycles
Irregular ovulation or anovulatory cycles
Hot flashes
Headaches and migraines
Breast swelling, pain, and/or tenderness

Especially when these symptoms occur in the week or so leading up to your period (aka PMS), they can be a sign of low progesterone, particularly in relation to estrogen.

What causes low progesterone?

You may have guessed it: not ovulating regularly is the top cause of low progesterone. Being on hormonal birth control also prevents your body from making its own progesterone- this can even continue for months after discontinuation of the pill or removal of a hormonal IUD.

Progesterone levels can also be insufficient due to chronic stress, under-eating, hypothyroidism, PCOS, and high prolactin. And even with sufficient progesterone levels, if estrogen is too high in relation (called “estrogen dominance), symptoms can arise.

How do you measure progesterone levels?

Considering the effects of progesterone on your overall health and pregnancy, it’s advisable to monitor certain signs and signals from your body that can provide insight into your production of progesterone.

Increased progesterone after ovulation causes a spike in your body’s basal temperature (BBT), which is your baseline temperature first thing in the morning before getting out of bed. A rise in temperature of at least ½ degree (F) confirms ovulation, and the sustained temp increase (for at least 10 days, 11-14 ideally), is a positive sign of sufficient progesterone production- especially in the context of an overall healthy menstrual cycle that’s relatively free of symptoms and any non-period spotting.

Another way to track ovulation is to measure your progesterone levels during the cycle. If the levels are high during the luteal phase of your cycle, it means that you have ovulated. But, if your levels remain low, you probably didn’t ovulate during that cycle.

The table below gives the normal progesterone levels during different stages of your menstrual cycle and pregnancy trimesters. Progesterone is typically measured as nanograms per milliliter (ng/mL).

Before you stress about getting your doctor to run the right markers or investing in an expensive at-home hormone panel, you can easily measure progesterone with the help of a fertility monitor like Inito. A convenient home testing device, Inito measures pregnancy hormones like progesterone (PdG), estrogen, luteinizing hormone (LH), and follicle stimulating hormone (FSH).

If you detect or even suspect lower than normal progesterone levels during the second half or luteal phase of your menstrual cycle, you can raise your concerns with your doctor for follow-up investigation and care.

How can you increase progesterone and maintain healthy levels?

Before you jump to adding supplemental progesterone, there are plenty of ways to help your body make enough on its own. Regular ovulation is key for this, which requires a healthy metabolism, adequate calories, and an abundance of nutrients. Stress is also an important focus since chronic stress can disrupt our hormonal signaling pathways.

Consider first making some changes to your nutrition and other lifestyle habits and giving your body time to restore and rebalance on its own! Monitoring your body through daily BBT tracking and and even testing your levels using the Inito can provide great feedback on your progress.

Especially if you’re wanting to conceive and suspect (or have confirmed) low progesterone, it’s helpful to allow your body to have at least 3 healthy ovulatory cycles before trying. The last thing you may want to hear is to wait more time, but in the end, the benefits are really worth it.

Your doctor may recommend taking exogenous progesterone sources to maintain healthy progesterone levels. This may involve:

Taking weekly progesterone injections between weeks 16 and 37 of your pregnancy or until delivery.
Using progesterone cream or gels directly on the skin or vaginal mucosa, which are formulated to mimic natural progesterone.
Progesterone supplements orally through pills or capsules, but not without due consultation from your doctor.
Progesterone suppositories inserted into the vagina.
Progesterone pessaries inserted into your vagina may be administered 2-3 times per day.

However, all these must be advised by your doctor and only then should you start using them under supervision.

Progesterone is a vital hormone and has many roles in menstruation and implantation while supporting the growth of a healthy baby in your uterus.

Being in tune with your body and tracking your hormone levels with an easy fertility monitor like Inito can help you detect fluctuations in progesterone that could affect your chances of getting (and staying) pregnant and supporting optimal hormone balance and vitality through life!

6 Benefits of Progesterone & How to Assess Your Levels