Menstrual Cycles, Ovulation, & Fertility Windows
You are not alone if you have ever felt like your body has a mind of its own!
One month your period is on time, the next it’s a surprise guest. You hear words like “ovulation” and “fertility window,” and it all feels like a biology test you didn’t study for.
All of this is completely normal though. It’s good to ask questions, and why you’ve stumbled on this post, right?
Many of us are taught what a period is, but hardly are we aware of our cycle, how ovulation impacts pregnancy rates, and things like “can I get pregnant if my cycle is irregular?”
When Can I Get Pregnant?
>This guide aims to answer any questions you may have, and help you understand your body’s natural cycle, starting with…
Your Menstrual Cycle: The 28-Day Myth
Think of your menstrual cycle not as a single event, but as a story your body tells over about 28 days.
But what if yours isn’t 28 days?
That’s perfectly fine. Truth be told, a “normal” cycle can actually range from 21 to 35 days.
Factors like stress, travel, and even changes in your diet can shift your timing. High stress, for example, can cause your period to be late up to a week. Sometimes longer.
Period symptoms also vary, and with varying degrees of pain. If this is something you experience often, there are a few ways you can reduce your period pain.
The biggest takeaway from this is that your body isn’t a machine; it’s a living, responding ecosystem.
To understand this better, here are four phases or “seasons” your cycle goes through.
The Four (4) Phases of the Menstral Cycle
Think of all four phases as “seasons.” This will help you understand each phase better.
Phase 1: Menstruation (Your Body’s “Winter”)
- What’s Happening: This is day one of your period. The lining of your uterus sheds because a pregnancy didn’t occur in the last cycle.
- Pregnancy Risk: Very low, but not zero.
Phase 2: The Follicular Phase (Your Body’s “Spring”)
- What’s Happening: After your period ends, your body gets to work preparing for a potential pregnancy. An egg begins to mature inside an ovary.
- Pregnancy Risk: It’s low at first, but starts to climb as you get closer to the main event.
Phase 3: Ovulation (Your Body’s “Summer”)
- What’s Happening: This is the big moment. The mature egg is finally released from the ovary and begins its journey.
- Pregnancy Risk: This is your peak fertility time.
Phase 4: The Luteal Phase (Your Body’s “Autumn”)
- What’s Happening: Your body waits to see if the egg will be fertilized. If not, hormone levels drop, and your body prepares to shed its lining, beginning the cycle all over again.
- Pregnancy Risk: Drops very quickly about 24 hours after ovulation.
The Answer to ‘When Can I Get Pregnant’: Understanding Ovulation
This is the part that causes the most confusion, so let’s clear up some myths and align the facts.
How Long Does Ovulation Actually Last?
The egg itself can only be fertilized for about 12 to 24 hours after it’s released.
It’s a very short window. So why, then, have you heard that you can get pregnant for several days each month?
Your “Fertility Window”: The Highest Chance of Getting Pregnant
Here’s the secret: it’s not just about the egg. Sperm can live inside your body for up to 5 days.
This means if you have sex on Monday, and you ovulate on Thursday, you could still become pregnant.
Your fertility window is the 5 days before you ovulate, the day of ovulation itself, and the day after ovulation.
This 7-day window is the only time during your cycle when you can get pregnant.
Read more: Fertility and Infertility Facts About Getting Pregnant
How Can I Tell If I’m Ovulating?
Your body often gives you subtle clues. Some of the most common signs of ovulation include:
- Change in Discharge: You might notice your vaginal discharge becomes clear, slippery, and stretchy—very similar to raw egg whites. This fluid helps sperm travel easily.
- Change in Temperature: Some people notice a very slight rise in their temperature, but you’d need a special thermometer to track this daily.
- Slight Cramping: A dull ache or twinge on one side of your lower abdomen is common.
- Increased Sex Drive: Your body’s natural way of telling you it’s go-time.
When Does Ovulation Happen?
Ovulation happens 14 days before your next menstrual period starts. This is important to remember, as you might have heard that ovulation happens 14 days after day 1 of your period.
The luteal phase (after ovulation) is more consistent in cycle length than the follicular phase (after your period/bleeding ends).
- The luteal phase usually lasts between 12 to 16 days, with an average of 14 days for most women
- The follicular phase varies for each person and even for every cycle
>It’s also important to note several factors that affect ovulation timing:
-
- Stress: physical, mental, or emotional stress can delay ovulation
- Excessive exercise: intense exercise can interfere ovulation, especially if you’re new to exercising and becoming more active
- Weight fluctuations: losing a lot of weight in a short period of time is one example of a weight fluctuation that could disrupt your hormonal balance, affecting ovulation
- Medical conditions: Thyroid disorders, hormonal imbalances, and conditions like Polycystic Ovary Syndrome (PCOS) can cause irregular ovulation
- Age: As you get older, your body’s hormonal balances change too. This is especially seen in women approaching menopause.
>If you want to track your ovulation (apart from noticing physical signs), you can subtract 14 days from your menstrual cycle:
- If you have a 28-day cycle: 28 days – 14 = 14; ovulation typically happens on day 14
- If you have a 32-day cycle: 32 days – 14 = 18; ovulation typically happens on day 18
Important: These calculations are just estimates and provide a good idea of when ovulation happens. They are not; however, 100% accurate.
>If you want to get an accurate reading, you have a couple of options:
- Basal body temperature charting: Your resting body temperature usually rises slightly (around 0.5-1 degree Fahrenheit) after ovulation due to the increase in progesterone.
- Cervical Mucus Monitoring: Your cervical mucus changes in consistency throughout your cycle. Around ovulation, it often becomes clear, slippery, and stretchy, similar to raw egg whites.
- Ovulation Predictor Kits (OPKs): These at-home urine tests detect a surge in Luteinizing Hormone (LH), which typically occurs 24-36 hours before ovulation. They’re also the most accurate predictors of ovulation.
- Schedule an appointment with your gynecologist: Your gynecologist can provide a more in-depth explanation of your menstrual cycle, along with the best/recommended approach for tracking ovulation.
“But My Cycle is Irregular. What Does That Mean?”
An irregular cycle is when your period or menstrual cycle deviates from the normal pattern of period frequency, duration, or flow.
>As noted, the average menstrual cycle is between 21 to 35 days. But with regards to your menstrual cycle length:
- If your period happens less than 21 days apart
- If your period happens more than 35 days apart
- Your menstrual cycle length varies month after month (e.g., one cycle is 28 days, next month is 37 days, then the month after is 40 days)
There could be several factors that could also contribute to an irregular cycle. For a proper evaluation, it’s best to get a checkup.
With regards to getting pregnant, tracking your ovulation (calendar method) isn’t a reliable approach if you have an irregular cycle.
This also doesn’t mean you can’t get pregnant. Even with an irregular menstrual cycle, ovulation still occurs.
Paying attention to your body’s physical signs—like your discharge— also becomes the most powerful tool you have.
You Have Questions? Women’s Aid Center Has Answers.
>This can be a lot to take in. Here are some of the most common questions we hear at our clinic.
Can you get pregnant on your period?
It’s very unlikely to get pregnant on your period, but not impossible, especially if you have a shorter cycle and have sex near the end of your period.
For example, if you have a shorter cycle (21 days), it’s safe to say you ovulate around day 7. Given that your fertility window is 5 days before you ovulate, having sex during this period can increase your chances of getting pregnant
How soon after my period can I get pregnant?
It depends on how long your cycle is. If you have a short cycle (e.g., 21 days), you could be ovulating just a few days after your period ends, making your fertility window start very early.
Do I need to use an ovulation calculator or app?
They can be helpful tools if your cycle is very regular, but they are just estimates. Learning your body’s own signs is often more accurate and empowering. Aside from OPKs, monitoring your cervical fluid/mucus is a proven method in determining whether you’re ovulating or not.
I had unprotected sex and I’m worried I might get pregnant. What do I do?
First, don’t panic. You have options. Emergency contraception/birth control (like the morning-after pill) is available. If you’ve missed your period, the first step is to take a pregnancy test to be sure. Reading about birth control facts will also help you gain a better understanding of the risks involved in pregnancy.
What Else Should I Know?
Understanding your cycle is a huge first step toward feeling in control of your reproductive health.
But we know that sometimes, life brings you questions and decisions you weren’t planning for. If you’re feeling worried or unsure about a possible pregnancy, we’re here to support you with confidential, non-judgmental care.
Here at Women’s Aid Center in Chicago, you have several options available, including abortion pill services and birth control options if you’re not ready for a pregnancy just yet.
If you prefer a more private, 1-on-1 approach to discuss your options, call us at (773) 725-4232 or schedule an appointment whenever you’re ready to talk.
Last Updated on July 11, 2025 by Womens Aid Center Chicago