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Understanding Ovulation and Fertile Period

What is Ovulation?

Understanding the Ovulation cycle, fertile period and most fertile days in a menstrual cycle greatly improves the chances of getting pregnant. Ovulation is the term used to describe the process that typically occurs once during each menstrual cycle when hormonal fluctuations stimulate one of the ovaries to release an egg. Following this release, the egg proceeds down the fallopian tube, where it has the potential to encounter a sperm and undergo fertilization. It is useful to know when ovulation is likely to occur, as a woman is most fertile during this period, and more likely to conceive.

What happens during Menstrual Cycle ?

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In the first half of the cycle, levels of estrogen start to rise, and makes the lining of the uterus (womb) grow and thicken. Simultaneously, an egg or ovum within one of the ovaries begins to mature. Around day 14 in a typical 28-day menstrual cycle, the egg is released from the ovary, an event known as ovulation.

Once released, the egg travels through the fallopian tube to reach the uterus. Hormone levels rise, playing a crucial role in preparing the uterine lining for potential pregnancy. The window of highest fertility for a woman is typically the three days leading up to or including the day of ovulation. It’s worth noting that women with menstrual cycles shorter or longer than the average 28 days may experience ovulation before or after the 14th day.

Conception occurs if the egg is fertilized by a man’s sperm and attaches itself to the uterine wall. If fertilization does not take place, the egg disintegrates. Subsequently, hormone levels drop, leading to the shedding of the thickened uterine lining during the menstrual period.

What happens during ovulation?

The ovulation process is defined by a period of elevated hormones during the menstrual cycle. It can be divided into 3 phases:

  • The periovulatory or follicular phase: During this phase, a layer of cells surrounding the ovum begins to mucify, or become more like mucus, and expand. The uterus lining begins to thicken.
  • The ovulatory phase: Enzymes are secreted and form a hole, or stigma on the ovary. There is a peak in the LH (luteinizing hormone) that triggers the release of ovum and its network of cells from the ovary into the fallopian tube. This is the window of fertility, typically lasts from 24 to 48 hours.
  • The postovulatory or luteal phase: Progesterone is released from the corpus luteum, which is the remnant of the ovarian follicle from which the egg was released. In the event of fertilization, the egg will implant into the uterine wall. In contrast, an unfertilized egg gradually ceases hormone production and dissolves within approximately 24 hours.

How to calculate Ovulation?

 Most women begin to menstruate between the ages of 10 to 15 years. At the same time, they begin to ovulate and become able to conceive. This is a phase known as the menarche.

  • Ovulation typically ceases after menopause, which usually occurs around the ages of 50 to 55. However, it still occurs in the period leading up to menopause, known as peri-menopause.
  • A menstrual cycle is defined from the onset of menstrual bleeding, referred to as day 1 of one menstrual period, to the commencement of menstrual bleeding in the next cycle.
  • An average menstrual cycle for women lasts between 28 and 32 days, but some women may experience significantly shorter or longer cycles.
  • The release of the egg generally takes place 12 to 16 days before the anticipated start of the next period.
  • Ovulation can be determined by either starting with the first day of the last menstrual period (LMP) or by calculating 12-16 days from the next expected period.
  • Most women ovulate anywhere between Day 11 and Day 21 of their cycle, counting from the first day of the LMP. This timeframe is often referred to as the “fertile period” of a woman’s cycle because sexual intercourse during this window increases the likelihood of pregnancy.
  • For most women ovulation is likely to happen around the middle of the cycle. However there is lot of variability in length of menstrual cycle among women, and with in cycles in same individual. Even in women with fairly regular cycles the day of ovulation can vary by +- 3 days.
  • It is important to track your cycle and you may use Ovulation Calculator to help identify peak fertile days.
  • Ovulation Calculator on this web site uses the results from multiple studies and accurately calculates the chances of ovulation for each day of the cycle. It gives you range of days in which you are most likely to ovulate. The chances of ovulation are high in the middle of this range and low near start and end days of this range.

Don’t women ovulate on the 14th day after their period starts ?

Unfortunately, this is a myth that many, including healthcare professionals, still believe. The notion of the “14th-day” likely stems from either an average calculation of when all women ovulate or simply dividing a 28-day cycle in half. However, this method is not a reliable way to pinpoint ovulation because numerous women do NOT experience ovulation on the 14th day of their cycle.

The day of ovulation varies from one woman to another and can even fluctuate from one month to the next within an individual’s cycle. In the case of a woman with a 28-day cycle, the ovulation window spans from day 11 through day 21 of the cycle. Ovulation may take place on any single day within this timeframe.

Did you know…

That most of the online ovulation calculators and fertility apps are often wrong or misleading?

Internet is littered with many ovulation tracker or fertility applications. But will you believe that most of these are often wrong or misleading. Here is a simple litmus test. We know that WHO (World Health Organization), recommends the Standard Days Method or SDM as a viable method of contraception having effectiveness of 95% when used correctly. Standard days method is recommended for women who have cycle length between 26 to 32 days. SDM recommends days 8 to 19 of a women’s mensural cycle as fertile period.

Most of the fertility apps determine a woman’s fertile window based on the assumption that ovulation happens on 14th day of the cycle and most fertile days are the ovulation date and the five preceding days. So out of total 12 potentially fertile days many couples could be missing critical opportunities for conception each month. For some, the added stress and frustration of months of unsuccessful attempts could be due in part to these false assumptions.

Now if you try our Advanced Ovulation Calculator with cycle length of 28 days, it will identify a fertile period of 10 days from day 9 to day 18 of the cycle. To be more accurate, it’s important to note that there are also possibilities of conception on day 8 and 19. However, we have deliberately omitted these days from consideration, as the likelihood of conception during this time is notably low, estimated at less than 2%. This clearly indicates that our application is much more precise and accurate.

Women who want to use our calculator for getting pregnant can follow the fertility period identified in the results. However, women who want to use it as contraception tool may also add one day on each side in the days to avoid intercourse.

 Ovulation Symptoms

To estimate when ovulation occurs, we must look for following signs of ovulation.

  • Increased Cervical Mucus: One of the most significant indicators is a change in cervical mucus. It transforms throughout your cycle, becoming more copious and stretchy, akin to raw egg whites during your most fertile days.
  • Heightened Senses: During ovulation, our senses become more attuned to male pheromones, resulting in increased attraction. Your sense of taste and even vision may become more acute.
  • Libido Changes: Some women experience a boost in their sex drive during ovulation. High estrogen and testosterone levels signal that your body is fertile, triggering an increased desire for intimacy.
  • Ovulation Pain: As the egg is released from the ovary, some women may feel a dull, achy sensation in the pelvis or lower abdomen. This discomfort is generally short-lived, lasting only a few hours.
  • Temperature Shift: Monitoring your basal body temperature can help track ovulation. Before ovulation, your temperature will slightly drop, followed by an increase of about half to one degree after ovulation, reflecting higher progesterone levels.
  • Spotting or Bleeding: As estrogen levels dip, the uterine lining may decrease slightly, potentially leading to minor vaginal bleeding. This should not be confused with implantation bleeding, which is a distinct occurrence.
  • Sensitive Breasts: While breast tenderness is often associated with PMS, some women may experience it as early as ovulation.
  • Bloating: Elevated estrogen during ovulation can lead to water retention, causing abdominal bloating, and sometimes swelling in the fingers and feet.
  • Nausea and Headaches: Rapid hormonal shifts during ovulation may trigger nausea and headaches, especially in women with slight hormonal imbalances.
  • Cervix Position Changes: Although many may not be familiar with their cervix’s location, during ovulation, it tends to be higher, softer, and more open in preparation for potential implantation.

 How can ovulation be detected?
Best Ovulation Calculator Ovulation Calendar

There are several tools that can be used to detect when a woman is ovulating.

  • Ovulation Calculators are tools that help individuals estimate their fertile window and identify the most likely days for ovulation based on information about their menstrual cycle. These calculators typically require you to input the first day of your last menstrual period (LMP) and the average length of your menstrual cycle. Please note that these calculators provide estimates and predictions and should not be considered a guarantee of ovulation. It’s essential to understand that individual variations and health conditions can impact your menstrual cycle and ovulation. If you’re trying to conceive, it’s a good idea to use these tools as a general guideline and consider additional methods.
  • basal thermometer can be used to track the subtle temperature increase. These can be purchased online or at most drug stores.
  • Some women feel a mild ache or pang of pain in the lower abdomen. This is called Mittelschmerz pain. It may last between a few minutes and a few hours.
  • Finally, ovulation predictor kits, available from drug stores, can detect the increase in luteinizing hormone (LH) in the urine just before ovulation.

What are most fertile days in menstrual cycle ?

An egg can survive in the Fallopian tube for about 24 hours after ovulation. A man’s sperm can remain viable within a woman’s body for approximately 3 days, and in certain cases, up to 5 days, following sexual intercourse. Pregnancy can occur when sexual activity takes place anywhere from 5 days prior to ovulation up to 1 day after ovulation. The highest likelihood of pregnancy arises when live sperm are present in the fallopian tubes at the time of ovulation.

Can I have a period and still not have ovulated?

Having a period does not always indicate that ovulation has taken place. In certain cases, women may encounter what’s known as an anovulatory cycle, signifying the absence of ovulation. Within an anovulatory cycle, women may undergo some bleeding that resembles a menstrual period, but, in reality, it does not represent a genuine period. This bleeding is caused by either a buildup in the uterine lining that can no longer sustain itself or by a drop in estrogen. The main way to decipher if ovulation is, in fact, taking place is by tracking your basal body temperature, and by transvaginal ultrasound.


Dr Sobia Mohyuddin

MCPS, FCPS, MRCOG, Consultant Obstetrics & Gynaecology

Doctor Sobia Mohyuddin is a highly skilled and experienced Obstetrician and Gynecologist, with 25 years of training and experience in renowned, large institutions. She holds the position of Associate Professor and Fellow at the College of Physicians and Surgeons Pakistan. She is also a member of the Royal College of Obstetricians and Gynecologists (UK).

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