Signs of Ovulation: How to Know When You're Fertile

Cervical Mucus Changes

Cervical mucus is the most reliable physical sign of approaching ovulation. Your cervical mucus changes throughout your cycle in response to estrogen levels, and learning to recognize these changes can help you identify your fertile window days before ovulation occurs.

How Cervical Mucus Changes Through Your Cycle

After your period ends, you may notice little to no cervical mucus—your vagina may feel dry. As estrogen rises during the follicular phase, mucus production increases and goes through several stages:

Egg White Cervical Mucus (EWCM)

The most fertile type of cervical mucus is often called "egg white cervical mucus" because it resembles raw egg whites. This mucus:

• Is clear or slightly cloudy
• Stretches between your fingers an inch or more without breaking
• Feels slippery and lubricative
• May be abundant enough to notice in your underwear

This type of mucus creates a sperm-friendly environment, helping sperm survive and swim toward the egg. When you notice EWCM, you are at or approaching peak fertility. For a deeper look at how to use mucus tracking for conception, see our full guide to cervical mucus and fertility.

How to Check Cervical Mucus

You can observe cervical mucus by:

• Noticing discharge on toilet paper when you wipe
• Checking your underwear throughout the day
• Reaching inside the vagina to collect mucus from near the cervix
• Paying attention to how you feel (wet vs. dry sensation)

The best sample typically comes from the cervix itself, as external mucus may be mixed with vaginal secretions. Check at the same time each day for consistency.

What If You Don't See EWCM?

Not every woman produces obvious egg white mucus, and that doesn't necessarily mean you're not ovulating. Some women have less abundant mucus or don't notice the external signs. Look for any mucus that's wetter, clearer, or stretchier than your baseline. Staying hydrated can help with mucus production. If you're concerned about your mucus patterns, consider supplementing your observations with ovulation predictor kits for an additional data point.

Ovulation Pain (Mittelschmerz)

About 20% of women experience ovulation pain, known by the German term "mittelschmerz" (meaning "middle pain"). This pain occurs around the time the egg is released from the ovary.

What Ovulation Pain Feels Like

Mittelschmerz can vary significantly between women and even from cycle to cycle:

• Location: Lower abdomen, on one side (the side where ovulation is occurring)
• Sensation: Sharp, sudden twinge; dull ache; cramping; or pressure
• Duration: Can last from a few minutes to 24-48 hours
• Intensity: Usually mild to moderate, rarely severe

What Causes Ovulation Pain

The exact cause isn't fully understood, but theories include:

• Swelling of the follicle before it releases the egg
• The rupture of the follicle when the egg is released
• Fluid or blood released during ovulation irritating the abdominal lining
• Fallopian tube contractions

Using Ovulation Pain for Timing

If you experience mittelschmerz, it can serve as a helpful ovulation indicator, but with caveats:

• The pain may occur before, during, or after the egg is released
• By the time you feel pain, ovulation may have already occurred
• The pain can switch sides from month to month
• Not every twinge is ovulation pain—other conditions can cause similar sensations

Mittelschmerz is most useful when combined with other signs (like cervical mucus changes) to confirm you're in your fertile window.

When Pain May Indicate a Problem

Mild ovulation pain is normal, but consult a healthcare provider if you experience:

• Severe pain that disrupts daily activities
• Pain lasting more than a couple of days
• Pain accompanied by fever, nausea, or unusual discharge
• Pain that occurs at times other than mid-cycle

Understanding Mittelschmerz: A Deep Dive

While we touched on ovulation pain above, mittelschmerz deserves a closer look because it is one of the few ovulation signs you can feel in real time. Understanding the nuances of this symptom can help you distinguish normal mid-cycle discomfort from something that warrants medical attention.

Left Side vs. Right Side Ovulation Pain

A common question is whether pain on one side means the corresponding ovary is ovulating. Generally, yes—the side where you feel mittelschmerz usually corresponds to the ovary releasing an egg that cycle. However, it is important to know that ovulation does not strictly alternate between ovaries each month. Research published in Human Reproduction has shown that the right ovary tends to ovulate slightly more often than the left, and some women report pain more frequently on one side across multiple cycles. If you consistently feel pain on the same side, it does not necessarily indicate a problem, but mentioning it at your next gynecological visit is a good idea.

What the Research Says About Its Cause

Several hypotheses attempt to explain why mittelschmerz occurs. The most widely accepted explanation involves the combination of follicular swelling and rupture. As the dominant follicle grows to about 20 mm before ovulation, it stretches the surface of the ovary, which can cause a sensation of pressure or a dull ache. When the follicle ruptures to release the egg, a small amount of follicular fluid and sometimes blood spills into the peritoneal cavity. This fluid can irritate the peritoneum—the membrane lining the abdomen—causing localized pain that may last from minutes to a day or two. According to a review in StatPearls (NCBI Bookshelf), the pain is considered a normal physiological process and does not indicate damage to the ovary.

Duration and Intensity Variations

For most women, mittelschmerz is brief—a sharp twinge lasting seconds to minutes. However, some women experience a dull, crampy ache that persists for up to 48 hours. The intensity tends to remain mild to moderate. If you track your pain carefully, you may notice it correlates well with your BBT temperature shift the following day, which can help confirm ovulation timing. Keeping notes about the side, intensity, and duration in a fertility journal or fertility tracker app can reveal patterns over several cycles.

When Ovulation Pain Is Abnormal

While mild to moderate mid-cycle pain is usually harmless, certain patterns can signal an underlying condition. Severe ovulation pain that leaves you unable to perform daily activities, recurs with worsening intensity, or is accompanied by heavy bleeding, fever, or vomiting should be evaluated by a healthcare provider. Conditions that can mimic or worsen mittelschmerz include:

• Endometriosis: Endometrial tissue outside the uterus can cause intense pelvic pain, especially around ovulation and menstruation. If mid-cycle pain is significantly impacting your quality of life, endometriosis is worth discussing with your doctor.
• Ovarian cysts: Functional cysts (follicular or corpus luteum cysts) occasionally cause pain during or after ovulation. Most resolve on their own, but large or persistent cysts may require monitoring.
• Pelvic inflammatory disease (PID): Infection-related pelvic pain can occur at any point in the cycle and is typically accompanied by fever, abnormal discharge, or pain during intercourse.
• Ectopic pregnancy: One-sided pelvic pain with a missed period should always be evaluated urgently.

If you are unsure whether your mid-cycle pain falls within the normal range, it is always wise to consult a healthcare professional for peace of mind.

Cervical Position Changes

Your cervix undergoes changes throughout your menstrual cycle that reflect your fertility status. While this sign requires internal checking and some practice to interpret, it can provide valuable information about ovulation timing.

How the Cervix Changes

During your fertile window, your cervix becomes:

• Softer: Like lips rather than the tip of your nose
• Higher: Rises in the vaginal canal and may be harder to reach
• Open: The os (opening) widens slightly
• Wetter: More mucus is present

These changes create a more welcoming environment for sperm. The acronym SHOW (Soft, High, Open, Wet) is often used to remember the fertile cervix characteristics.

After Ovulation

After ovulation, the cervix returns to a non-fertile state:

• Firm: Like the tip of your nose
• Low: Easier to reach
• Closed: The opening becomes tighter
• Dry: Less mucus present

How to Check Your Cervix

To check cervical position:

1. Wash your hands thoroughly
2. Find a comfortable position (squatting, one leg raised, or lying down)
3. Insert one or two fingers into your vagina
4. Feel for the cervix at the top of the vaginal canal
5. Note its position, firmness, and whether it feels open or closed

Check at the same time each day, as cervical position can vary throughout the day. It takes several cycles of practice to interpret these changes accurately. Combining cervical position data with your cervical mucus observations gives you a more complete picture of your fertility status.

Increased Libido

Many women experience a noticeable increase in sexual desire around ovulation. This is your body's way of encouraging reproduction during your most fertile time.

The Hormonal Connection

Rising estrogen levels and the surge in luteinizing hormone (LH) before ovulation can boost libido. Research shows that women tend to:

• Initiate sex more often around ovulation
• Feel more sexually attractive
• Be more interested in romantic and sexual activity
• Have more sexual fantasies

Physical Attractiveness Studies

Interestingly, research also suggests that women may be perceived as more attractive during their fertile window. Studies have found subtle changes in voice, scent, and appearance that peak around ovulation, though these effects are small and not universally observed.

Using Libido as a Sign

While increased libido can correlate with ovulation, it's not a precise indicator. Many factors affect sex drive, including stress, relationship dynamics, sleep, and overall health. However, if you notice a consistent pattern of increased desire mid-cycle, it may be a helpful supplementary sign of your fertile window.

Breast Tenderness

Some women experience breast tenderness or sensitivity around ovulation. This is due to hormonal fluctuations, particularly rising estrogen and the effects of progesterone after ovulation.

Timing of Breast Changes

Breast tenderness related to the menstrual cycle can occur at different times:

• Around ovulation: Rising estrogen can cause mild sensitivity
• After ovulation (luteal phase): Progesterone can cause more pronounced tenderness
• Before your period: Often part of PMS symptoms

What to Notice

Breast changes around ovulation may include:

• Tenderness to touch
• Feeling of fullness or heaviness
• Nipple sensitivity
• Mild swelling

Distinguishing Ovulation Tenderness from Other Causes

Breast tenderness alone isn't a reliable ovulation indicator because it can have many causes. However, if you consistently notice breast changes at a specific point in your cycle and it correlates with other signs (like cervical mucus changes), it may help confirm your fertile window.

Other Signs and Symptoms

Beyond the primary signs, some women notice other changes around ovulation:

Light Spotting

A small percentage of women experience light spotting around ovulation, sometimes called "ovulation spotting." This can occur when the follicle ruptures and releases the egg. The spotting is typically:

• Very light (a small amount of pink or brownish discharge)
• Brief (lasting only a day or two)
• Occurring around mid-cycle

Not everyone experiences ovulation spotting, and it can also be caused by other factors. If you have unusual bleeding, consult a healthcare provider.

Heightened Senses

Some women report enhanced sense of smell around ovulation. Research has shown that women's olfactory sensitivity can increase during the fertile window, possibly making them more attuned to certain scents, including potential mates' pheromones.

Bloating

Hormonal fluctuations around ovulation can cause mild water retention and bloating in some women. This is typically less pronounced than pre-menstrual bloating but may be noticeable.

Increased Energy

Rising estrogen during the follicular phase often brings increased energy levels. Many women feel their best in the days leading up to ovulation, experiencing greater motivation, mental clarity, and physical energy.

Positive OPK Results

While ovulation predictor kits (OPKs) are a tool rather than a physical sign, a positive result indicates that the LH surge is occurring and ovulation is likely within 24-36 hours. This is one of the most reliable ways to predict ovulation before it happens. Digital OPKs like those from Clearblue can be particularly easy to interpret for beginners.

Ovulation Signs vs. PMS Symptoms: How to Tell the Difference

One of the most common sources of confusion when tracking your cycle is distinguishing ovulation signs from premenstrual syndrome (PMS) symptoms. Both involve hormonal shifts, and some symptoms—like breast tenderness, bloating, and mood changes—can overlap. However, the timing, hormonal drivers, and specific characteristics differ in important ways.

The key distinction comes down to when in your cycle symptoms appear. Ovulation signs occur around mid-cycle (roughly days 12-16 of a 28-day cycle), driven by rising estrogen and the LH surge. PMS symptoms appear in the luteal phase (roughly days 21-28), driven by progesterone dominance and the subsequent hormone withdrawal before menstruation. Understanding these cycle phases is essential for interpreting your body's signals correctly.

Comparing Ovulation Signs and PMS Symptoms

The Timing Test

If you are unsure whether what you are experiencing is an ovulation sign or a PMS symptom, the simplest test is timing. Count the days since your last period started. If you are around the midpoint of your cycle (for most women, days 12-16), the symptom is more likely related to ovulation. If you are in the final week before your expected period (days 21-28 in a typical cycle), PMS is the more likely cause. Tracking your cycle length over time with an ovulation calculator or fertility app makes this distinction much easier.

For a thorough understanding of when in your cycle ovulation occurs, our guide on how many days after your period you ovulate breaks this down in detail.

Tracking Your Ovulation Signs

To get the most benefit from ovulation signs, track them systematically over several cycles.

What to Track

Record daily observations of:

• Cervical mucus: Type, amount, and sensation
• Basal body temperature: Take before getting out of bed
• Cervical position: If you're comfortable checking
• Physical symptoms: Ovulation pain, breast tenderness, spotting
• OPK results: If using ovulation predictor kits
• Other observations: Libido, energy, mood

Combining Signs

The most reliable approach is to look for multiple signs pointing to ovulation. For example:

• Egg white cervical mucus + positive OPK = ovulation is imminent
• EWCM + ovulation pain + temperature rise the next day = ovulation confirmed
• High, soft, open cervix + fertile mucus = fertile window

Using an App or Chart

Many fertility apps allow you to log multiple signs and will interpret patterns for you. Paper charts also work well and may help you see patterns more clearly. Our ovulation calculator can estimate your fertile window based on your cycle length, and you can then confirm with physical signs.

Patterns Over Time

After tracking for 2-3 cycles, you'll likely notice your personal patterns. You may find that you consistently get EWCM starting 2 days before ovulation, or that you always experience ovulation pain on one particular side. These individual patterns make tracking more reliable over time.

Day-by-Day Ovulation Signs Timeline

Understanding exactly when each ovulation sign appears can help you anticipate your fertile window before it arrives. Below is a detailed day-by-day timeline showing how your body changes from five days before ovulation through two days after. Use this as a reference alongside your own fertility tracking to spot your personal patterns.

Ovulation Symptoms vs. PMS Symptoms

Distinguishing between ovulation-related symptoms and premenstrual syndrome (PMS) is one of the most common challenges women face when learning to track their cycles. Both involve hormonal shifts, and several symptoms -- including breast tenderness, bloating, mood changes, and pelvic discomfort -- overlap significantly. The critical difference lies in timing, the specific hormonal drivers involved, and the subtle character of each symptom.

According to the Planned Parenthood guide on PMS, premenstrual symptoms are driven by the drop in estrogen and progesterone that occurs in the late luteal phase, whereas ovulation symptoms coincide with the estrogen peak and LH surge at mid-cycle. The NHS PMS overview notes that PMS symptoms typically begin 1-2 weeks before your period and resolve once menstruation starts.

Detailed Symptom-by-Symptom Comparison

The Definitive Test: Timing in Your Cycle

When in doubt, check where you are in your cycle. If you are approximately 12-16 days from the start of your last period (in a typical 28-day cycle), the symptom is very likely ovulation-related. If you are in the final 7-10 days before your expected period, PMS is the more probable explanation. Using an ovulation calculator to estimate your ovulation day, combined with physical sign tracking, makes this distinction straightforward over time.

Cervical Position as a Fertility Sign

While cervical mucus is the most commonly tracked fertility sign, cervical position itself provides a powerful secondary confirmation of where you are in your cycle. The cervix physically transforms throughout the menstrual cycle in response to hormonal changes, and learning to read these transformations adds another layer of confidence to your fertility tracking. Many women who practice the symptothermal method include cervical position as a third biomarker alongside mucus and temperature.

The SHOW Method Explained

Fertility educators use the acronym SHOW to describe the characteristics of a fertile cervix. When the cervix displays all four SHOW traits simultaneously, you are in or approaching your fertile window:

Cervical Position by Cycle Phase

The following reference table shows how cervical position changes across the four main phases of the menstrual cycle:

Note: Day counts are based on a typical 28-day cycle. Your personal cycle may be shorter or longer. Adjust these ranges based on your own ovulation timing.

Tips for Checking Cervical Position

• Consistency is key: Check at the same time each day, ideally in the evening, as the cervix can shift position throughout the day due to activity and gravity.
• Use the same position: Squat, place one foot on the toilet seat, or lie down -- pick one position and use it every time so comparisons are accurate.
• Clean hands: Always wash your hands thoroughly before and after checking to prevent introducing bacteria.
• Be patient: It typically takes 2-3 full cycles of daily checking before you can confidently distinguish the changes. The differences are subtle at first.
• Record your findings: Use a simple scale (e.g., 1-3 for height, soft/medium/firm for texture) in your fertility tracking app or chart.
• Combine with mucus observations: When you check cervical position, note the mucus present at the cervix at the same time -- this gives you both data points in one check.

The Symptothermal Method

The symptothermal method (STM) is widely regarded as the gold standard of fertility awareness-based methods. By combining basal body temperature (BBT), cervical mucus observations, and calendar calculations, STM gives you both prospective signals (ovulation is approaching) and retrospective confirmation (ovulation has occurred). This multi-layered approach achieves significantly higher accuracy than any single-sign method used alone.

The World Health Organization (WHO) fertility awareness guidelines recognize the symptothermal method as an effective approach when taught correctly. A landmark study by Frank-Herrmann et al. (2007), published in Human Reproduction, found a perfect-use failure rate of just 0.4% per year, making it comparable in effectiveness to hormonal contraception when used to avoid pregnancy.

The Three Pillars of the Symptothermal Method

Each component of STM provides a distinct piece of the fertility puzzle:

How to Practice the Symptothermal Method

Effectiveness and Reliability

When practiced correctly, the symptothermal method is remarkably effective. Key research findings include:

• Perfect-use failure rate: 0.4% per year (Frank-Herrmann et al., 2007)
• Typical-use failure rate: Approximately 2-12% per year, depending on the population studied and level of instruction received
• For conception: Couples using STM to time intercourse during the identified fertile window have conception rates comparable to those using OPK-based timing

The American College of Obstetricians and Gynecologists (ACOG) notes that multi-sign fertility awareness methods are substantially more reliable than single-indicator approaches such as calendar-only or mucus-only methods.

Getting Started: Practical Steps

• Invest in a quality BBT thermometer: Choose one that reads to at least 0.01 degrees Fahrenheit (or 0.05 degrees Celsius). Digital BBT thermometers with memory recall features are ideal.
• Pick a charting method: Use a dedicated fertility tracking app (such as Kindara, Fertility Friend, or Read Your Body) or a paper chart. Log your data every day.
• Start with two signs: Begin by tracking just cervical mucus and BBT for 2-3 cycles. Add cervical position checking once you are comfortable with the first two.
• Be consistent: Take your temperature at the same time each morning. Check mucus at the same times each day. Consistency produces the clearest patterns.
• Consider formal instruction: Many certified STM instructors offer online courses. Structured learning accelerates your ability to interpret your charts confidently.
• Be patient: It typically takes 2-3 complete cycles to feel confident interpreting your signs. Use that learning period alongside other methods if needed.

Whether you are trying to conceive, practicing natural family planning, or simply seeking deeper body literacy, the symptothermal method empowers you with daily, actionable insights into your unique cycle.

Ovulation Symptoms Day by Day

Understanding what happens in your body each day around ovulation can help you pinpoint your most fertile time with greater precision. According to Mayo Clinic, recognizing the progression of fertility signs across the days surrounding ovulation is one of the most effective natural methods for timing conception. The timeline below maps out what you can expect from five days before ovulation (O-5) through two days after (O+2), covering cervical mucus changes, BBT patterns, OPK results, and physical sensations.

Keep in mind that this timeline represents a typical pattern -- your personal experience may vary. Some women notice signs earlier or later, and not everyone experiences every symptom. The key is to track your own patterns over 2-3 cycles so you learn what is normal for you. Using a fertility tracking app alongside our ovulation calculator can help you log and compare daily observations effectively.

This day-by-day pattern illustrates why the Royal College of Obstetricians and Gynaecologists (RCOG) recommends that couples trying to conceive should have intercourse every 2-3 days throughout the cycle, or at minimum during the days when these fertile signs are present. Tracking multiple signs simultaneously -- a practice called the symptothermal method -- gives you the most complete fertility picture.

Ovulation Signs After Stopping Birth Control

If you have recently stopped using hormonal birth control and are watching for ovulation signs, you may be wondering how long it will take for your natural cycle to return. According to Healthline, the timeline varies significantly depending on the method you were using. Some women ovulate within weeks, while others may wait several months for regular cycles to resume. The table below provides general timelines based on research, though individual variation is substantial.

While waiting for ovulation to return, you can begin practicing the skills of cervical mucus monitoring and BBT tracking even before your cycle has fully regulated. This allows you to recognize the first signs of returning fertility. If your cycles have not returned within the timelines below, consult a fertility specialist for evaluation.

As noted by WebMD, the type and duration of birth control use can influence how quickly natural hormone cycles resume. During the transition period, ovulation predictor kits are particularly valuable because they detect the LH surge regardless of whether your cycles have regularized. Keep in mind that your first few post-pill cycles may be slightly longer or shorter than your eventual pattern -- track when you ovulate relative to your period for at least 3 cycles before relying on calendar predictions.

Tracking Your Personal Ovulation Pattern

Every woman's ovulation pattern is unique, and the most powerful fertility tool you have is a record of your own body's signals across multiple cycles. According to research referenced by the RCOG, women who track multiple ovulation signs for at least 3 cycles can predict their fertile window with significantly higher accuracy than those using calendar methods alone. The table below provides a monthly tracking template you can adapt for your own use.

To use this template, record your observations each day starting from cycle day 1 (first day of your period). Focus on the five key parameters: cervical mucus quality, BBT reading, OPK result, cervical position, and any secondary symptoms. After 2-3 cycles, you will begin to see your personal pattern emerge.

This template assumes a 28-day cycle with ovulation around day 14 -- adjust the days for your own cycle length. If you have irregular cycles, start OPK testing earlier (around day 8-9) and continue until you get a positive or until your period arrives. For women with cycles ranging from 21-35 days, our guide on how many days after your period you ovulate provides cycle-specific ovulation estimates.

Related Reading

Continue exploring our complete library of fertility and ovulation guides:

• Ovulation Calculator -- Free tool to predict your fertile window and ovulation date
• About Ovulation Calculator -- Learn about our mission and methodology
• Fertile Window: When Are You Most Likely to Conceive?
• The Menstrual Cycle and Ovulation Explained
• Due Date Calculator Based on Ovulation Date
• How Many Days After Your Period Do You Ovulate?
• Basal Body Temperature and Ovulation
• Cervical Mucus and Fertility
• OPK Ovulation Predictor Kits
• Irregular Periods and Ovulation
• Ovulation With Irregular Periods
• The Four Phases of Your Menstrual Cycle Explained
• How Long After Ovulation Is Your Period?
• Due Date Calculation Methods Compared
• Clearblue Ovulation Calculator Guide
• Best Fertility Tracker Apps
• When to See a Fertility Specialist

Frequently Asked Questions

External Resources

For further reading on ovulation signs, fertility tracking, and reproductive health, the following trusted resources provide in-depth, medically reviewed information:

• Mayo Clinic: Getting Pregnant -- Signs of Ovulation -- Comprehensive overview of ovulation signs from one of the world's leading medical institutions.
• Planned Parenthood: Fertility Awareness Methods -- Clear, accessible guide to natural fertility tracking methods, including the symptothermal method.
• Cleveland Clinic: Ovulation -- Detailed medical article covering the ovulation process, signs, and common questions.
• NHS: Signs and Symptoms of Ovulation -- The UK National Health Service's patient-friendly guide to recognizing ovulation.
• PubMed: Effectiveness of the Symptothermal Method (Frank-Herrmann et al., 2007) -- The landmark research study on the symptothermal method's effectiveness.
• PubMed: Timing of Intercourse in Relation to Ovulation (Wilcox et al., 1995) -- Key research establishing the fertile window's duration and optimal conception timing.
• ACOG: Fertility Awareness-Based Methods of Family Planning -- The American College of Obstetricians and Gynecologists' official guidance on fertility awareness methods.
• WHO: Fertility Awareness-Based Methods of Family Planning -- The World Health Organization's guidelines and publications on natural family planning methods.

More From Ovulation Calculator

Continue learning about your cycle and fertility with these in-depth guides from our site:

• The Menstrual Cycle and Ovulation Explained -- A foundational overview of how the menstrual cycle works, the hormones involved, and what happens during each phase from menstruation through ovulation to the luteal phase.
• Menstrual Cycle Phases Explained in Detail -- A deep dive into the four phases of the menstrual cycle: menstrual, follicular, ovulation, and luteal. Understanding these phases is essential context for interpreting ovulation signs.
• How Many Days After Your Period Do You Ovulate? -- Practical guidance on calculating when in your unique cycle ovulation is most likely to occur, based on your period start date and cycle length.
• Clearblue Ovulation Calculator Guide -- If you are using or considering digital ovulation predictor kits, this guide covers how Clearblue and similar advanced OPKs work alongside natural sign tracking.

Sources

• Bigelow, J. L., Dunson, D. B., Stanford, J. B., Ecochard, R., Gnoth, C., & Colombo, B. (2004). Mucus observations in the fertile window: a better predictor of conception than timing of intercourse. Human Reproduction, 19(4), 889-892. PubMed
• Brott, N. R., & Le, J. K. (2022). Mittelschmerz. In StatPearls. StatPearls Publishing. NCBI Bookshelf
• Wilcox, A. J., Dunson, D. B., Weinberg, C. R., Trussell, J., & Baird, D. D. (2001). Likelihood of conception with a single act of intercourse: providing benchmark rates for assessment of post-coital contraceptives. Contraception, 63(4), 211-215. PubMed
• Gangestad, S. W., & Thornhill, R. (2008). Human oestrus. Proceedings of the Royal Society B, 275(1638), 991-1000. PubMed
• Frank-Herrmann, P., Heil, J., Gnoth, C., et al. (2007). The effectiveness of a fertility awareness based method to avoid pregnancy in relation to a couple's sexual behaviour during the fertile time. Human Reproduction, 22(5), 1310-1319. PubMed
• Wilcox, A. J., Weinberg, C. R., & Baird, D. D. (1995). Timing of sexual intercourse in relation to ovulation. New England Journal of Medicine, 333(23), 1517-1521. PubMed
• Stanford, J. B., White, G. L., & Hatasaka, H. (2002). Timing intercourse to achieve pregnancy: current evidence. Obstetrics & Gynecology, 100(6), 1333-1341. PubMed
• Fehring, R. J., Schneider, M., & Raviele, K. (2006). Variability in the phases of the menstrual cycle. Journal of Obstetric, Gynecologic & Neonatal Nursing, 35(3), 376-384. PubMed
• American College of Obstetricians and Gynecologists. Fertility Awareness-Based Methods of Family Planning. ACOG
• Mayo Clinic. Signs of Ovulation. Mayo Clinic
• Cleveland Clinic. Ovulation. Cleveland Clinic
• NHS UK. Signs and Symptoms of Ovulation. NHS
• Planned Parenthood. Fertility Awareness Methods. Planned Parenthood
• World Health Organization. Family Planning / Contraception Methods. WHO