1068
Request Call Back
Contact
1068
Ovulation: What It Is, Signs, Cycle Timing and When It Starts
Published on: Sep 10, 2026
TABLE OF CONTENTS
Ovulation is the central event of the menstrual cycle. Everything before it prepares for it; everything after it responds to whether fertilisation occurs. For women trying to conceive, ovulation timing is the single most practically important piece of cycle knowledge. In India, where PCOS, thyroid disorders and nutritional factors affecting ovulation are prevalent, understanding what ovulation is, when it occurs and how to track it helps women take control of their reproductive health.
What Is Ovulation
Ovulation is the release of a mature egg (oocyte) from a dominant follicle in one of the two ovaries. It occurs once per menstrual cycle in women with regular cycles typically in the middle of the cycle. The released egg travels down the fallopian tube. If sperm are present at the time of ovulation fertilisation can occur. The egg is viable for approximately 12 to 24 hours after release. If the egg is unfertilised it degenerates and the cycle moves into the luteal phase.
Ovulation is triggered by a sharp surge in luteinising hormone (LH) from the anterior pituitary gland causing the dominant follicle to rupture and release the egg. Hormonal, nutritional and systemic factors influence the timing regularity and quality of ovulation.
What Happens During Ovulation?
Ovulation is not an instantaneous event but the culmination of a hormonal sequence spanning the first half of the cycle.
Follicle development: From the first day of menstruation, follicle-stimulating hormone (FSH) stimulates several follicles in the ovaries. Over the course of 10 to 14 days, one follicle (the dominant follicle, or Graafian follicle) grows larger than the rest and begins producing increasing amounts of oestrogen
Oestrogen rise and LH surge: As oestrogen levels rise to a peak, the hypothalamus and pituitary respond with a sharp, rapid surge in LH (and a smaller FSH surge). This LH surge (lasting 24 to 48 hours) directly triggers ovulation and causes the dominant follicle to rupture and release the oocyte.
Egg release and transport: The oocyte is released into the peritoneal cavity and immediately swept up by the fimbriae at the end of the fallopian tube with the cilia (lining the fallopian tube) propel it toward the uterus. Fertilisation, if it occurs, happens within the fallopian tube, typically in the ampullary region.
When Does Ovulation Start After Your Period
In a 28-day cycle, ovulation occurs approximately on day 14 from the first day of the last menstrual period (LMP). Very few women have consistently 28-day cycles. Ovulation timing varies with cycle length, as it is the follicular phase that varies, while the luteal phase remains relatively constant at 14 days.
A practical guide to estimating ovulation day is to subtract 14 from the expected cycle length. For a 30-day cycle ovulation likely occurs around day 16. For a 35-day cycle, it is around day 21. For a 24-day cycle, around day 10. This estimate is least reliable in women with irregular cycles including those with PCOS, thyroid dysfunction or hypothalamic amenorrhoea.
Ovulation Phase and Periovulatory Phase
The ovulation phase refers to the approximately 24-hour window during which the egg is released and viable. The periovulatory phase is a broader concept covering the days immediately surrounding ovulation.
The periovulatory phase spans approximately five days before ovulation to the day of ovulation itself. This window is the fertile window, wider than a single day because sperm can survive in the female reproductive tract for three to five days. The two to three days before ovulation are when the probability of conception is highest.
Some sources distinguish between the preovulatory phase (final follicular maturation, beginning with the LH surge), the ovulatory phase (egg release) and the postovulatory or luteal phase (corpus luteum and progesterone secretion). This distinction is useful in assisted reproduction, where timing of interventions depends on the patient's position in this sequence.
Common Ovulation Symptoms
Not every woman notices symptoms when she ovulates. For those who do, the most common are as follows.
Changes in cervical mucus: One of the most reliable signs of approaching ovulation. As oestrogen levels rise in the late follicular phase, cervical mucus becomes increasingly clear, slippery and stretchy, resembling raw egg white.
Mild pelvic or lower abdominal pain (Mittelschmerz): Brief one sided pain or cramping in the lower abdomen which you may feel around the time of ovulation.
Increased libido: Many women notice a natural increase in sexual desire in the days surrounding ovulation. This is thought to be driven by the peak in oestrogen and LH around ovulation.
Types of Ovulation
Ovulation is clinically described by its regularity, quality, and occurrence pattern.
Regular (ovulatory) cycles: Ovulation that occurs consistently in each cycle within a predictable window. Most women with regular cycles between 24 and 38 days are ovulating regularly. Regular ovulation is a necessary prerequisite for fertility.
Anovulation: The absence of ovulation. Anovulatory cycles may still involve menstrual-like bleeding (anovulatory bleeding), when oestrogen stimulates the uterine lining without a luteal progesterone rise. PCOS is the most common cause of anovulation. Other causes include thyroid disorders, hyperprolactinaemia and excessive exercise.
Oligo-ovulation: Infrequent ovulation, occurring fewer than eight times per year (a clinical feature of PCOS and other hormonal disorders).
Induced ovulation: Ovulation triggered by medication in fertility treatment. Ovulation induction is a standard part of fertility management at IVF centres.
Which Hormone Induces Ovulation
Luteinising hormone (LH) (produced by the anterior pituitary gland) is the hormone that directly triggers ovulation. The LH surge, a rapid and substantial rise in LH over 24 to 48 hours, causes the mature follicle to rupture and release the egg. Ovulation typically occurs 24 to 36 hours after the LH surge.
LH does not act in isolation. The LH surge is triggered by the rising oestrogen produced by the dominant follicle, a positive feedback loop. FSH also surges briefly alongside LH just before ovulation and contributes to final oocyte maturation.
This is why urinary LH detection is the most practical method of predicting ovulation. A positive test indicates that ovulation is likely within the next 24 to 36 hours.
How to Track Your Ovulation Cycle
Several methods are available to track ovulation (ranging from simple observation to technology assisted monitoring).
Cervical mucus monitoring (Billings method): Track changes in cervical mucus throughout the cycle. The appearance of clear, stretchy, slippery mucus indicates the approach of ovulation. You do not need any equipment and it is widely used in family planning.
Basal body temperature charting: Measure BBT every morning before getting out of bed, at the same time each day using a basal thermometer (rise of approximately 0.2 to 0.5 degrees Celsius following the follicular phase baseline indicates that ovulation has occurred). The rise is retrospective and confirms ovulation but does not predict it.
Ovulation predictor kits (OPKs): Urine-based LH tests that detect the LH surge 24 to 36 hours before ovulation. Begin testing a few days before the expected ovulation window
Ultrasound follicle tracking (folliculometry): A transvaginal ultrasound series performed by a gynaecologist to visualise follicle development and confirm ovulation. Folliculometry is the gold standard for confirming ovulation and timing of intercourse or insemination.
Conclusion
Ovulation is the pivotal event of the menstrual cycle, the point at which fertility briefly peaks and around which the hormonal activity of the entire cycle is organised. Knowing when it occurs, how to recognise its signs, what hormones drive it and how to track it accurately is valuable for any woman trying to conceive, trying to avoid pregnancy naturally or simply seeking to understand her cycle.
FAQs
What is ovulation and what does it mean?
Ovulation is the release of a mature egg from a dominant follicle in one of the ovaries. Triggered by a surge in luteinising hormone (LH) from the pituitary it occurs once per cycle. It marks the window when conception is possible.
What happens during ovulation?
The dominant follicle ruptures and releases the egg, which is swept into the fallopian tube by the fimbriae. The ruptured follicle transforms into the corpus luteum and secretes progesterone. If fertilisation does not occur menstruation begins.
When does ovulation start after your period?
In a 28-day cycle, ovulation typically occurs around day 14. Ovulation timing varies significantly in women with PCOS or thyroid disorders.
What is the periovulatory phase?
The periovulatory phase is the fertile window spanning five days before your ovulation to the day of ovulation. Sperm can survive in the reproductive tract during this period (two to three days before ovulation is a period when your conception probability becomes maximum).
What are the common signs of ovulation?
Clear, stretchy cervical mucus resembling raw egg white is the most consistent sign. Other signs include mild one-sided pelvic pain (Mittelschmerz), increased libido and light spotting. Basal body temperature rises slightly after ovulation but only confirms it in retrospect.
What hormone triggers ovulation?
Luteinising hormone (LH) triggers ovulation. A sharp LH surge from the pituitary gland lasting 24 to 48 hours causes the dominant follicle to rupture & release the egg. Ovulation in your body can happen between one to two days after this LH surge.
How long does ovulation last?
The egg is released over a process lasting minutes to a few hours. It remains viable for approximately 12 to 24 hours.
What are the different types of ovulation?
Different types are:
Regular ovulation occurs in women with normal cycles.
In anovulation no egg is released but women experience menstruation.
Oligo-ovulation is infrequent ovulation fewer than eight times per year.
Induced ovulation is triggered by medications.
Can you feel ovulation happening?
Some women can experience Mittelschmerz, a brief, one-sided lower abdominal pain at mid-cycle. Changes in cervical mucus and increased libido are also perceptible signs. Some women experience no noticeable symptoms at all.
How can I calculate my ovulation period?
Subtract 14 from your expected cycle length to estimate ovulation day. For irregular cycles ovulation predictor kits (OPKs) are the most practical method. Cervical mucus monitoring and BBT charting are also reliable.
References
1. Lessey BA, Young SL. What exactly is endometrial receptivity?. Fertil Steril. 2019;111(4):611–7. https://doi.org/10.1016/j.fertnstert.2019.02.009
2. Holesh JE, Bass AN, Lord M. Physiology, ovulation. StatPearls. 2023; updated 2023 May 1. https://www.ncbi.nlm.nih.gov/books/NBK441996/
3. Vigil P, Lyon C, Flores B, Rioseco H, Serrano F. Ovulation, a sign of health. Linacre Q. 2017;84(4):343–55. https://doi.org/10.1080/00243639.2017.1394053
4. Practice Committee of the American Society for Reproductive Medicine. Use of clomiphene citrate in infertile women: a committee opinion. Fertil Steril. 2013;100(2):341–8. https://doi.org/10.1016/j.fertnstert.2013.05.033
5. Unuane D, Tournaye H, Velkeniers B, Poppe K. Endocrine disorders and female infertility. Best Pract Res Clin Endocrinol Metab. 2011;25(6):861–73. https://doi.org/10.1016/j.beem.2011.08.001
