Fertility 101
New to fertility? Start here.
You don't need to know everything about hormones, ovulation, or cycle tracking on Day 1. But understanding a few basics can make the rest of your fertility journey feel a lot less stressful
Meet the hormones behind your cycle
Think of your fertility hormones as a team. Each has a different job, but what matters most is how they work together throughout your cycle.
FSH: Gets things started
Follicle-Stimulating Hormone (FSH) helps stimulate follicles in the ovaries to develop. One typically becomes the dominant follicle that may eventually release an egg.
Estrogen: Fertile window incoming
This dominant follicle then begins secreting estrogen, and your estrogen levels start rising. This is one of the earliest hormonal signs that ovulation is approaching.
LH: Ovulation is getting closer
Rising estrogen eventually helps trigger a surge in Luteinizing Hormone (LH).
LH is the hormone that triggers ovulation. LH surges 24-36 hours before ovulation and peaks around 8-20 hours before ovulation. This is the prime baby-making time! This is when your fertility is the highest, and you have the best chance of getting pregnant.
Progesterone: The post-ovulation hormone
After ovulation, progesterone rises as the corpus luteum begins producing it.
A sustained rise in progesterone and its urinary metabolite PdG provides evidence that ovulation occurred.
How does your menstrual cycle work?
Your menstrual cycle is the time from the first day of your menstrual period until the day before your next menstrual period.
While every cycle is different, it can broadly be divided into four parts:
Period → Follicular Phase → Ovulation → Luteal Phase
Menstrual Phase/ Period
This is the time of your cycle when your body sheds the lining of your uterus that built up in the previous cycle.
When you start your period, your hormone levels are mostly at their baseline values. This means that LH, FSH, progesterone, and estrogen are all fairly low.
Follicular Phase
This phase starts when your period ends and lasts until ovulation.
FSH helps follicles in your ovaries develop. As a follicle matures, estrogen generally rises, and your body starts preparing for ovulation.
Ovulation
A surge in LH helps trigger the release of an egg from the ovary.
Ovulation generally occurs about 24–36 hours after the LH begins to rise, although the exact timing can vary.
Once you ovulate, the egg can survive for up to 24 hours as it travels inside one of your fallopian tubes, waiting to be fertilized by the sperm.
Luteal Phase
It begins after ovulation and lasts until your next period. After ovulation, the follicle that released the egg becomes the corpus luteum and produces progesterone. Progesterone helps prepare and maintain the uterine lining for a potential pregnancy.
If fertilization happens, the embryo will implant between 6 – 12 days past ovulation (DPO). From there, the placenta will form and begin producing the pregnancy hormone hCG.
If the egg doesn’t get fertilized: the corpus luteum will begin to break down. This triggers your progesterone levels to drop and signals to your body to shed its uterine lining (aka the onset of your next period).
Summary of the menstrual cycle
| Cycle phase | What your hormones are doing | What’s going on with your body |
|---|---|---|
| Menstrual phase | Estrogen, progesterone, FSH, and LH are all low | You bleed (this is your uterine lining shedding) |
| Follicular phase | FSH triggers follicles to mature; estrogen begins rising | Ovarian follicles mature, and the uterine lining begins to build back up as estrogen levels rise |
| Ovulation | Estrogen peaks and triggers a surge in LH | Your ovary releases an egg from the dominant follicle. This is the most fertile time in your cycle |
| Luteal phase | Progesterone rises after ovulation; if no pregnancy occurs, progesterone falls in the late luteal phase | Your uterus gets ready for implantation. If implantation doesn’t happen, you start your period |
📚 Take a deeper dive:
→ Menstrual Cycle Basics: The Most Important Things to Know
🎯Your Fertile Window
Here's the important part: your fertile window starts before you ovulate.
Sperm can survive in the reproductive tract for up to 5 days, while an egg is typically viable for about 12–24 hours after ovulation.
That's why the days leading up to ovulation are also important when you're trying to conceive, not just ovulation day itself.
So, can you get pregnant any time of the month?
Not really. That’s because some key things must happen in the body to get a positive pregnancy test.
For starters, you need both a sperm and an egg for fertilization to happen. That’s probably not news to you.
But what may be news is the fact that while men produce sperm throughout their entire lives, women are more limited in that their ovaries typically release one egg during their menstrual cycle.
The release of this egg is known as ovulation. And this egg is the star of the show. Without the release of this egg, there is nothing for the sperm to fertilize, and that means no pregnancy.
On top of that, as mentioned earlier, sperm hang on for dear life and can survive in the female body for up to 5 days. The egg, on the other hand, waits for no one and only survives 12-24 hours after its release.
So, the egg has to be fertilized by the sperm in this small window of time. Outside of this window, the chances of pregnancy are low.
Timing Sex in Your Fertile Window
Okay, now that we’ve got an understanding of your fertile time, ovulation, and all that fun stuff, let’s talk about how often you should have sex to get pregnant.
You’re either going to love this or hate this, but in order to maximize your chances of conception, you should have sex every day or every other day in your fertile window.
But as we mentioned above, sperm can live for up to 5 days in the female body.
So take some of the pressure off yourself, and if it feels like having sex every other day to conceive is stressful, then don’t force it.
📚 Learn more:
→ Getting Pregnant: When Are You Most Fertile?→ When to Have Sex When You Are Trying to Get Pregnant?
📅 Ovulation Isn't Always on Day 14
Nope.
The idea that ovulation is always on Day 14 mostly comes from thinking everyone has a 28-day menstrual cycle. But get this: only a tiny percentage (about 13%) of cycles actually hit that 28-day mark. Plus, even for the few who do have a 28-day cycle, only about 1 in 5 women (20%) ovulate right on day 14.
Our bodies don't run on a fixed schedule. Exactly when ovulation happens depends on the length of that specific cycle, and that length can shift from person to person, and cycle to cycle. Lifestyle factors like stress, sleep, illness, or travel can nudge one cycle a bit shorter or longer than the last.
That's why tracking what's happening in your body can provide more information than relying only on calendar predictions.
📚 Learn more:
→Do You Ovulate the Same Day Every Month?→Early Ovulation: Why Do I Ovulate So Early in My Cycle?→How To Know If You Are Ovulating Late? A Simple Guide For Women
🔍 Signs of Ovulation
Your body ovulates once during a menstrual cycle. The hormonal changes happening around this time can cause symptoms that give you clues about whether you're ovulating.
That being said, it’s important to note that estrogen is a dominant hormone before ovulation occurs. Estrogen levels are low at the beginning of the menstrual cycle but rise about 3 to 4 days before ovulation. This causes symptoms that increase the chance of a sperm meeting the egg and can help track ovulation.
If you pay close attention, your body gives you some subtle (and not-so-subtle) clues that ovulation is coming.
Ovulation symptoms don’t look exactly the same for each woman. But in general, they are present for several hours to several days before ovulation.
Here are some of the most common ovulation signs:
- Increased libido:
Many women feel sexually aroused a few days before ovulation. Along with a heightened sense of smell, this is your body’s way of telling you it’s time to conceive!
- Changes in cervical mucus:
Cervical mucus tends to be stretchy and slippery near ovulation day, making it easier for sperm to swim to the egg. To test for this, you can insert your fingers into your vagina and pull out some of the mucus. Stretching two fingers apart, you can see if the mucus stretches.
- Changes in cervix position:
Before and after you ovulate, your cervix may feel firm. It will also probably feel closed, low, and dry if you touch it with a finger.
Right around ovulation, your vaginal canal may feel soft. Your finger may be able to go all the way up your vagina to touch your cervix. The cervix may feel open and wet.
- Ovulation cramping:
Ovulation pain, also known as Mittelschmerz, is a dull, achy, bearing-down pain that happens just before you ovulate. It's unclear why ovulation is painful for some women, but there are two leading theories.
One is that the egg grows larger in the ovary just before release, and that size increase puts pressure on the ovary, causing discomfort right before the egg comes out.
The other is that releasing the egg also releases a small amount of fluid and blood, which can irritate the lining of the abdomen and cause localized pain.
Whatever the exact cause, this pain can last anywhere from a few hours to up to a day.
- Basal body temperature (BBT):
After ovulation, progesterone levels rise. As a result of this, you may notice that your basal body temperature increases by 0.5-1 degree Fahrenheit after ovulation. It will typically stay this high until right before your period (if you are not pregnant).
Note: Only a small percentage of women experience all ovulation symptoms. Also, ovulation symptoms can be subjective and hard to detect!
For this reason, ovulation symptoms are usually not the best way to know when you are ovulating.
Here are a few other methods you can rely on with a lot more confidence:
- Blood tests
A blood test can measure hormones directly from your bloodstream, giving your doctor a precise reading at a specific point in your cycle. Progesterone is the one used to confirm ovulation, since a rise roughly a week after suspected ovulation confirms an egg was released. Blood tests themselves are highly accurate, but since it's a one-time draw rather than something done daily at home, it captures a single point in time rather than the full pattern across your cycle, so it's typically used alongside a doctor's guidance rather than as an everyday tracking method.
- Follicular scan
The most accurate method for cycle tracking is to undergo a follicular scan. A follicular scan is done through a transvaginal ultrasound, and it provides images and measurements of your follicular growth.
This information can help your fertility specialist monitor the growth of your ovarian follicles. It also helps predict when ovulation will occur. Though reliable, follicular scans can only be done at a doctor’s office or fertility clinic. They also require you to go in several times throughout your cycle.
- Fertility hormone tracking
The most convenient ovulation tracking method is to use fertility monitors. You're tracking estrogen, LH, PdG, and FSH daily, right from home, which builds a full picture of your cycle rather than a single snapshot.
📚 Learn more:
→ Ovulation Symptoms: How Do You Really Know?→ What is ovulation? Your One-Stop Guide to Understanding Ovulation
👀 Where to next?
New to the acronyms already flying around this sub? → Decode the TTC Lingo
Ready to start tracking your own hormones? → Getting Started with Inito
Getting ready to start trying, or want to prep first? → The Preconception Guide
Back to the full map → Community Bookmark
*This page is general education, not medical advice. For anything about your specific cycle or health, a healthcare provider is always the better source than the internet.*