Your menstrual cycle is a monthly hormonal process that prepares your body for pregnancy. Most cycles last 21-35 days(average ~28). Ovulation, when an ovary releases an egg, is the single most important event for fertility. The egg survives about 12-24 hours, while sperm can live up to 3-5 days, so the “fertile window” is roughly the five days before ovulation plus the day of ovulation. This guide explains each phase in plain language, how to recognize ovulation, ways to track it, and when to see a clinician.
The ovulation cycle, part of the menstrual cycle, typically lasts ~28 days but can range from 21 to 35 days. It involves hormonal changes that prepare the body for pregnancy. Here’s a general breakdown:
- Days ~1–5 (Menstrual Phase): This phase overlaps the beginning of the follicular phase. The cycle begins with menstruation, when the thickened uterine lining sheds due to a drop in progesterone. Hormones involved: Low estrogen and progesterone. The hypothalamus signals the pituitary gland to release follicle-stimulating hormone (FSH).
- Common symptoms:
- Cramping due to uterine contractions
- Low energy or fatigue
- Mood swings or irritability
- Breast tenderness may decrease
- Bloating
- Headaches
- Common symptoms:
- Days ~1–14 (Follicular Phase): FSH stimulates the ovaries to mature a handful of follicles. One becomes dominant and produces estrogen, which thickens the uterine lining (endometrium) in preparation for a possible embryo. Rising estrogen from the dominant follicle signals the hypothalamus to trigger an LH surge, which causes ovulation.
- Note: The follicular phase actually begins on Day 1 (overlapping with menstruation) and continues until ovulation.
- Common symptoms:
- Gradually increasing energy and motivation
- Clearer skin
- Improved mood and focus
- Cervical mucus starts to appear (cloudy, then egg-white-like near ovulation)
- Libido may start to rise
- Day ~14 (Ovulation): A sudden spike in LH causes the mature follicle to rupture, releasing an egg into the fallopian tube. This is the most fertile time of the cycle. The egg lives for 12–24 hours, but sperm can survive up to 5 days, creating a fertile window.
- Common symptoms:
- Mild pelvic or abdominal pain (mittelschmerz)
- Egg-white cervical mucus (very stretchy and clear)
- Slight increase in basal body temperature (after ovulation)
- Increased sex drive
- Breast tenderness
- Heightened sense of smell or taste
- Some report bloating or spotting
- Common symptoms:
- Day ~15–28 (Luteal Phase): After ovulation releases the egg, the ruptured follicle becomes the corpus luteum, which secretes progesterone. Progesterone stabilizes the uterine lining and inhibits further ovulation. If fertilization doesn’t occur, the corpus luteum breaks down, hormone levels drop, and the cycle restarts with menstruation.
- Common symptoms (can vary widely):
- Mood swings, irritability, or low mood (PMS)
- Fatigue or low energy
- Food cravings
- Bloating
- Breast tenderness/swelling
- Sleep disturbances
- Slight drop in libido
- Acne breakouts (due to hormone changes)
- Common symptoms (can vary widely):
| Phase | Typical days (~28-day cycle) | Key hormones | What you might notice |
| Menstrual | ~1–5 | Low estrogen & progesterone | Bleeding, cramps, tiredness |
| Follicular | ~1–14 | Rising FSH → estrogen | Energy rises, cervical mucus appears |
| Ovulation | ~14 | LH surge → ovulation | Mittelschmerz, egg-white mucus |
| Luteal | ~15–28 | Progesterone high | BBT rises, PMS symptoms possible |
The Fertile Window:
In a typical 28-day cycle, the fertile window spans approximately days 10–16, with ovulation usually around day 14. This is when unprotected intercourse is most likely to result in pregnancy.
Lifestyle Tips to Support Healthy Ovulation
Optimize ovulation naturally:
- Regular exercise (not excessive)
- Nutrient-rich diet
- Folate (leafy greens, legumes)
- B vitamins (whole grains, eggs, fish)
- Vitamin D (sunlight, fortified foods, fatty fish)
- Iron (lean meat, beans, fortified cereals)
- Omega-3 fatty acids (fish, walnuts, flaxseed)
- Sleep hygiene
- Managing stress (e.g., yoga, therapy, mindfulness)
Common signs of ovulation stage:
- Clear, stretchy cervical mucus (like egg whites)
- Mild abdominal pain (mittelschmerz)
- Slight increase in basal body temperature
- Breast tenderness
- Increased libido
How to track ovulation:
Naturally
- Basal Body Temperature
- Take your temperature first thing every morning before getting out of bed
- After ovulation, progesterone causes your temperature to rise by 0.5–1°F
- This confirms ovulation has occurred but doesn’t predict it in advance
- Best for: Understanding your patterns over time
- Cervical Mucus Monitoring
- Check your cervical mucus daily
- After period: Little to no mucus
- Approaching ovulation: Cloudy, sticky, or creamy mucus
- At peak fertility: Clear, stretchy, slippery mucus like raw egg whites
- After ovulation: Mucus dries up or becomes thick and sticky again
- Best for: Identifying your fertile window in real-time
- Check your cervical mucus daily
- Ovulation predictor kits
- These detect the LH surge in urine, signaling ovulation within 12–36 hours. False positives can occur in PCOS due to elevated baseline LH levels.
Hormone Tracking Devices
Rings (Tracks temperature and heart rate variability, which correlate with hormonal shifts.)
- Oura ring
- Femometer smart ring
Wrist Wearables
- Ava Fertility Bracelet
- Monitors skin temperature, pulse, and sleep patterns to predict fertile windows for regular cycles.
- Apple watch
- Fitbit
- Garmin watch
Medical Tools
- Ultrasound or blood test (doc)
- Transvaginal ultrasound can visualize follicle growth and confirm ovulation by observing the corpus luteum, typically used in fertility clinics.
- Ovusense vaginal sensor
- Measures core body temperature continuously, offering higher precision for irregular cycles.
AI-Powered Fertility Apps: Newer apps integrate AI to analyze cycle patterns, predict ovulation with higher accuracy, and provide personalized recommendations (e.g., Flo, Clue).
- Flo – uses machine-learning on your logged cycle/period/symptom data to predict fertile windows, ovulation, and provide personalized health insights.
- Clue – uses an algorithm (DOT/ML) on cycle history and logged signs to estimate ovulation/fertile windows and support conception tracking.
- Glow – uses advanced algorithms/AI on menstrual and fertility data to predict fertility windows, track ovulation, and give community and coaching support.
- Ovia – uses AI-powered guidance on cycle, symptom, and fertility sign data (temperature, fluid etc.) to personalize fertility-related insights and track your journey.
What Can Disrupt Your Cycle?
Lifestyle and Environmental Factors
Stress
- Chronic or acute stress can suppress the release of GnRH (gonadotropin-releasing hormone) from your hypothalamus, which in turn reduces FSH and LH production. This can delay ovulation or prevent it entirely, leading to longer cycles or missed periods.
Significant Weight Changes
- Both sudden weight loss and weight gain can disrupt your cycle. Low body weight or body fat (often seen with eating disorders, extreme dieting, or intense athletic training) can halt ovulation by reducing GnRH secretion. Conversely, excess weight can lead to hormonal imbalances that affect ovulation.
Extreme Exercise or Athletic Training
- High-intensity training or excessive exercise—especially when combined with low body fat or inadequate caloric intake—can suppress ovulation. This is common in competitive athletes, dancers, and long-distance runners and is often referred to as “hypothalamic amenorrhea.”
Eating Disorders
- Conditions like anorexia nervosa, bulimia, or restrictive eating patterns can severely disrupt the hormonal signals needed for ovulation. Recovery typically restores cycle regularity, though it may take time.
Poor Sleep or Irregular Sleep Patterns
- Disrupted sleep, shift work, or chronic sleep deprivation can interfere with the hormonal rhythms that regulate your menstrual cycle.
Exposure to Endocrine-Disrupting Chemicals
- Environmental toxins found in some plastics (BPA), personal care products (phthalates), pesticides, and industrial chemicals can interfere with hormone production and ovulation. While it’s difficult to avoid these entirely, minimizing exposure when possible may support hormonal health.
Illness or Infection
- Acute illness, fever, or infection can temporarily delay ovulation as your body prioritizes fighting off illness. Cycles typically return to normal after recovery.
Travel or Significant Schedule Changes
- Major time zone changes, disrupted routines, or significant life transitions can temporarily affect cycle timing, though this usually resolves once you’ve adjusted.
Medical Conditions
Polycystic Ovary Syndrome (PCOS)
- One of the most common hormonal disorders affecting people of reproductive age. PCOS is characterized by elevated androgens (male hormones), insulin resistance, and multiple small follicles on the ovaries. High LH levels and insulin resistance prevent follicles from maturing properly, leading to irregular or absent ovulation. Symptoms often include irregular periods, acne, excess hair growth, and difficulty conceiving.
Thyroid Disorders
- Both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid) can disrupt menstrual cycles. The thyroid hormones interact with reproductive hormones, and imbalances can lead to irregular ovulation, heavy or light periods, or absent menstruation.
Hyperprolactinemia
- Elevated levels of prolactin (the hormone responsible for milk production) can suppress ovulation. This can be caused by certain medications, pituitary tumors (usually benign), or other medical conditions. Symptoms may include irregular periods, milky nipple discharge (galactorrhea), and difficulty conceiving.
Primary Ovarian Insufficiency (POI)
- Also called “premature ovarian failure,” POI occurs when the ovaries stop functioning normally before age 40. This leads to irregular or absent ovulation, reduced estrogen production, and symptoms similar to menopause. It can be caused by genetic factors, autoimmune conditions, or medical treatments.
Hypothalamic Amenorrhea
- A condition where the hypothalamus slows or stops releasing GnRH, which disrupts the entire hormonal cascade needed for ovulation. This is often caused by stress, low body weight, excessive exercise, or a combination of these factors.
Endometriosis
- A condition where tissue similar to the uterine lining grows outside the uterus. While endometriosis doesn’t always directly prevent ovulation, it can cause inflammation and scarring that affects fertility and may be associated with irregular cycles.
Uterine Fibroids or Polyps
- While these typically don’t prevent ovulation, they can affect the uterine lining and menstrual flow patterns, sometimes causing heavier or irregular bleeding.
Medications and Treatments
Hormonal Birth Control
- Birth control pills, patches, rings, injections (Depo-Provera), implants, and hormonal IUDs work primarily by suppressing ovulation or altering the hormonal environment to prevent pregnancy. This is intentional and reversible—ovulation typically resumes within weeks to months after discontinuation, though the Depo-Provera shot may take longer (up to 18 months in some cases).
Antidepressants
- Some selective serotonin reuptake inhibitors (SSRIs) and other psychiatric medications can affect cycle regularity by influencing serotonin’s interaction with reproductive hormones. Not everyone experiences this side effect, and it shouldn’t prevent you from taking necessary medication—discuss any concerns with your doctor.
Antipsychotic Medications
- Many antipsychotics increase prolactin levels, which can suppress ovulation and cause irregular or absent periods. Your doctor can monitor prolactin levels and adjust medications if needed.
Corticosteroids
- Long-term use of corticosteroids (for conditions like autoimmune disorders or severe asthma) can disrupt the hypothalamic-pituitary-ovarian axis and affect ovulation.
Chemotherapy and Radiation
- Cancer treatments can temporarily or permanently damage ovarian function, depending on the drugs used, dosage, and your age at treatment. Fertility preservation options should be discussed before starting cancer treatment when possible.
Other Medications
- Certain medications for epilepsy, chronic pain, or other conditions may affect cycle regularity. Always inform your healthcare provider about all medications you’re taking if you’re experiencing cycle changes.
Age-Related Changes
Adolescence
- During the first few years after menarche (first period), cycles are often irregular as the hormonal system matures. Anovulatory cycles (cycles without ovulation) are common during this time.
Peak Fertility Years
- Fertility is typically highest from the late teens through the late 20s, with the most consistent ovulation patterns during this period.
Declining Fertility (Early to Mid-30s)
- Fertility begins to decline gradually around age 32 and more noticeably after age 35, as both egg quality and ovarian reserve decrease. Cycles may remain regular, but conception may take longer.
Perimenopause (Late 30s to Early 50s)
- The transition to menopause typically begins in the 40s but can start in the late 30s for some people. During perimenopause, ovarian reserve declines, and hormone levels fluctuate unpredictably. This leads to increasingly irregular cycles—some may be very short, others unusually long, and ovulation becomes less predictable. Eventually, menstruation stops entirely (menopause).
When to See Your Healthcare Provider
Schedule an appointment if you experience:
- Absent periods (amenorrhea) for 3 or more months when you’re not pregnant
- Very irregular cycles that consistently fall outside the 21–35 day range
- Sudden changes in cycle pattern, flow, or duration
- Severe menstrual pain that interferes with daily activities
- Very heavy bleeding (soaking through a pad or tampon every hour for several hours)
- Bleeding between periods or after intercourse
- Symptoms of hormonal imbalance such as excessive facial/body hair growth, severe acne, unexplained weight changes, or milk production from nipples when not breastfeeding
- Difficulty conceiving after:
- 12 months of trying (if under age 35)
- 6 months of trying (if age 35 or older)
- Concerns about any of the disruptions listed above
FAQ: Ovulation & Cycle Questions
Q: Can I ovulate more than once in a cycle?
A: No, you can’t ovulate multiple times on separate days. However, it’s possible to release more than one egg during a single ovulation event—within the same 24-hour window. This happens when multiple follicles mature and release eggs at the same time, which can lead to fraternal twins. It’s more likely in women who are older, have a genetic predisposition, or are undergoing fertility treatments like clomiphene.
Q: Do I always ovulate on Day 14?
A: Not necessarily. Ovulation timing can vary from cycle to cycle, even in people with regular periods.
Q: Can you get pregnant during your period?
A: It’s unlikely, but possible — especially with short cycles where ovulation happens soon after menstruation ends.
Q: Does birth control “reset” my cycle?
A: Hormonal birth control suppresses ovulation. Once stopped, it may take a few weeks to months for cycles to normalize or “reset”.
Q: How long does it typically take to get pregnant?
A: For couples under 35 having regular unprotected intercourse (2-3 times per week):
- About 30% conceive within the first month
- About 60% within 3 months
- About 75% within 6 months
- About 85-90% within one year
These statistics decrease with age, particularly after age 35. Other factors that affect conception time include overall health, existing medical conditions (like PCOS or endometriosis), lifestyle factors, and male fertility factors. If you’ve been trying for 12 months without success (or 6 months if you’re over 35), it’s time to consult a fertility specialist.
The menstrual cycle is more than just a monthly period — it’s a complex hormonal dance that prepares the body for potential pregnancy. Central to this cycle is ovulation, a key event that signals the release of a mature egg. Whether you’re looking to conceive, avoid pregnancy, or simply understand your body better, knowing how ovulation works is empowering.
Hormone and Phase Glossary:
Corpus Luteum
The temporary structure formed in the ovary after a mature follicle releases an egg during ovulation. The corpus luteum produces progesterone, which thickens and stabilizes the uterine lining (endometrium) to support a potential pregnancy. If fertilization doesn’t occur, it breaks down within 10–14 days, leading to a drop in progesterone and the start of menstruation.
Endometrium
The inner lining of the uterus that thickens during the menstrual cycle in response to rising estrogen and progesterone levels. It prepares to nurture a fertilized egg. If pregnancy doesn’t occur, the endometrium sheds during menstruation, marking the start of a new cycle.
Estrogen
A group of hormones (primarily estradiol) produced by the ovaries, particularly during the follicular phase. Estrogen stimulates the growth of the uterine lining, promotes follicle development, and triggers the luteinizing hormone (LH) surge that leads to ovulation. It also influences cervical mucus, making it thin and stretchy during the fertile window to aid sperm movement.
Follicle
A small, fluid-filled sac in the ovary that contains an immature egg. During the follicular phase, follicle-stimulating hormone (FSH) stimulates several follicles to grow, but typically only one (the dominant follicle) matures fully and releases an egg during ovulation.
Follicle-Stimulating Hormone (FSH)
A hormone released by the pituitary gland that stimulates the ovaries to develop follicles during the first half of the menstrual cycle (follicular phase). FSH helps prepare the egg for ovulation and supports estrogen production by the growing follicles.
Follicular Phase
The first phase of the menstrual cycle, spanning from the first day of menstruation (Day 1) to ovulation (around Day 14 in a 28-day cycle). During this phase, follicle-stimulating hormone (FSH) promotes the growth of ovarian follicles, one of which becomes dominant and produces estrogen to thicken the uterine lining.
Gonadotropin-Releasing Hormone (GnRH)
A hormone released by the hypothalamus in the brain that signals the pituitary gland to produce follicle-stimulating hormone (FSH) and luteinizing hormone (LH). GnRH regulates the menstrual cycle by controlling the timing and release of these hormones, which drive follicle development and ovulation.
Hypothalamus
A region of the brain that controls the menstrual cycle by releasing gonadotropin-releasing hormone (GnRH). The hypothalamus responds to stress, weight changes, and other factors, which can influence cycle regularity by altering GnRH secretion.
Luteal Phase
The second half of the menstrual cycle, occurring after ovulation (Days 15–28 in a 28-day cycle). During this phase, the corpus luteum produces progesterone to maintain the uterine lining. If the egg isn’t fertilized, progesterone levels drop, triggering menstruation and the start of a new cycle.
Luteinizing Hormone (LH)
A hormone released by the pituitary gland that triggers ovulation. A surge in LH, prompted by high estrogen levels, causes the mature follicle to rupture and release an egg. LH also supports the formation of the corpus luteum, which produces progesterone during the luteal phase.
Menstrual Cycle
The monthly hormonal process (typically 21–35 days) that prepares the female body for pregnancy. It includes four main phases: menstruation, the follicular phase, ovulation, and the luteal phase. The cycle is driven by interactions between the hypothalamus, pituitary gland, and ovaries, regulating hormone levels and ovulation.
Menstrual Phase
The phase of the menstrual cycle (Days 1–5) when the uterine lining (endometrium) sheds, resulting in menstrual bleeding. This occurs due to a drop in progesterone and estrogen levels when pregnancy doesn’t happen, signaling the start of a new cycle.
Ovary
One of two reproductive organs in females that produce eggs and hormones (estrogen, progesterone). Each ovary contains thousands of follicles, which house immature eggs. During each cycle, one or more follicles mature, leading to ovulation.
Ovulation
The release of a mature egg from a dominant follicle in the ovary, typically around Day 14 in a 28-day cycle. Triggered by a surge in luteinizing hormone (LH), ovulation marks the most fertile period, when the egg is available for fertilization for 12–24 hours.
Pituitary Gland
A small gland at the base of the brain that releases follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in response to signals from the hypothalamus. These hormones regulate follicle development, ovulation, and progesterone production.
Progesterone
A hormone produced by the corpus luteum after ovulation. Progesterone thickens and stabilizes the uterine lining during the luteal phase to prepare for a potential pregnancy. If fertilization doesn’t occur, progesterone levels drop, triggering menstruation.
Uterus
The muscular organ where a fertilized egg implants and grows during pregnancy. The uterus builds up its inner lining (endometrium) during the menstrual cycle to support a potential embryo. If pregnancy doesn’t occur, this lining sheds during menstruation.
Additional Resources
American College of Obstetricians and Gynecologists (ACOG)
Menstrual Cycle and Ovulation Information
https://www.acog.org/womens-health/faqs/your-menstrual-cycle
Mayo Clinic
Ovulation and Fertility Tracking
https://www.mayoclinic.org/healthy-lifestyle/getting-pregnant/in-depth/ovulation/art-20044228
Office on Women’s Health (U.S. Department of Health & Human Services)
Menstrual Cycle Basics
https://www.womenshealth.gov/menstrual-cycle
Planned Parenthood
Birth Control and Fertility Awareness Methods
https://www.plannedparenthood.org/learn/birth-control
American Society for Reproductive Medicine (ASRM)
Patient Education Resources
https://www.reproductivefacts.org
References
American College of Obstetricians and Gynecologists. (2023). Your Menstrual Cycle. Retrieved from https://www.acog.org/womens-health/faqs/your-menstrual-cycle
Mayo Clinic. (2024). Ovulation Signs: When Is Conception Most Likely? Retrieved from https://www.mayoclinic.org/healthy-lifestyle/getting-pregnant/in-depth/ovulation/art-20044228
Speroff, L., & Fritz, M. A. (2011). Clinical Gynecologic Endocrinology and Infertility (8th ed.). Lippincott Williams & Wilkins.
Reed, B. G., & Carr, B. R. (2018). The Normal Menstrual Cycle and the Control of Ovulation. In K. R. Feingold et al. (Eds.), Endotext. MDText.com, Inc. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK279054/
Trussell, J. (2011). Contraceptive failure in the United States. Contraception, 83(5), 397-404.