Posted on April 20th, 2020by Dr. Matthew Ledermanin Fertility

How Do I Know When I'm Ovulating?

The menstrual cycle is the monthly hormonal cycle women experience in preparation for pregnancy. The cycle is divided into two phases, which include the follicular and the luteal phase. The follicular phase, which begins with day 1 of bleeding (period), is often referred to as LMP (last menstrual period) and ends on the day prior to the LH (luteinizing hormone) surge. Ovulation, which is the release of the egg from the ovary, typically occurs around day 14 of the cycle, and if the egg is not fertilized, hormone levels eventually decrease, and the cycle begins again with the start of another period around day 28. This phase is referred to as the luteal phase. A cycle is counted from day 1 of a period to the first day of the following period. The average menstrual cycle is approximately 28 days, but can range from 21-35 days. In a regular menstrual cycle, the anterior pituitary gland in the brain secretes FSH (follicle stimulating hormone), which stimulates a follicle in the ovary to grow and secrete estradiol (estrogen). Mid cycle, there is an LH surge produced form the anterior pituitary gland in the brain, resulting in ovulation and release of the egg from the ovary.

In women trying to conceive, ovulation prediction is commonly used to time intercourse. There are a few different ways to evaluate the presence and timing of ovulation, which includes charting of the menstrual cycle, basal body temperature monitoring, measurement of serum progesterone levels, and detection of an LH surge in urine kits.

One of the simplest methods to monitor ovulation is menstrual cycle charting. This simple technique involves tracking the first day of one’s period for a few months in a row. In general, cycles between 25-35 days are usually ovulatory. Tracking of symptoms may also be helpful when monitoring the menstrual cycle, but ovulation symptoms can vary from woman to woman with some experiencing no symptoms. Symptoms may include an increase in thin cervical stretchy mucus (“egg white”) around the time of ovulation, mid cycle twinge of pain or cramps (mittelschmerz), and premenstrual symptoms, such as menstrual cramps, breast tenderness, fluid retention, and appetite or mood changes, may be indicative of an ovulatory cycle. Some women may also experience an increase in sex drive and mid cycle spotting.

Another method to evaluate ovulation is basal body temperature monitoring. After ovulation occurs, the corpus luteum in the ovary (the follicle in the ovary which releases the egg) secretes progesterone, which results in the hypothalamus in the brain to increase body temperature. Therefore, monitoring of daily body temperature can be used to determine if ovulation occurred. Women utilizing this technique are advised to use a mercury thermometer, which is able to detect a one-tenth of a degree temperature difference, which electronic thermometers may be less accurate at detecting. Woman utilizing this method are advised to take their temperature first thing in the morning upon awakening by placing the thermometer under the tongue. In a regular menstrual cycle, there is a rise in body temperature of approximately 0.5 degrees 1-2 days following the LH surge, which then persists for approximately 10 days (luteal phase of the menstrual cycle). Although daily temperature changes can retrospectively identify ovulation, they cannot be used to time intercourse in a given cycle. Many women may find this method frustrating, as it can sometimes be difficult to interpret if ovulation occurred and requires daily charting, although use of apps are often helpful.

Another method to evaluate ovulation is measurement of serum progesterone in the mid-luteal phase, typically on days 18-24. If the initial progesterone concentration is low, one can repeat the serum progesterone levels a few days later to confirm if ovulation occurred.

For couples actively trying to conceive, the highest probability of conceiving is with intercourse one to two days prior to ovulation. As a result, identifying this fertile period to assist with intercourse timing will maximize the likelihood of conceiving. Urinary LH Kits, or OPK (ovulation predictor kit), can be used to detect LH surges, predict ovulation, and therefore assist with timing of intercourse. In general, rise in serum LH occurs approximately 36 hours before the egg is released from the ovary, and an LH surge in the urine can be detected 12 hours after it appears in the serum. Women utilizing this method should start testing 1-2 days prior to the expected surge by checking first thing in the morning around the same time each day. It is advised to limit fluid intake at the time of checking so urine is more concentrated, allowing an easier detection of the LH surge. Fertility monitors can assist with identifying your five most fertile days by monitoring both urinary LH and estrogen levels to identify the two peak fertile days, and the one-to-five fertile days leading up to them. There are certain conditions that may yield false-positive results, meaning no ovulation has occurred despite detection of an LH surge. These conditions include polycystic ovary syndrome (PCOS), primary ovarian insufficiency, and menopause. The ability to detect a urinary estradiol rise may help minimize false-positive results.

Although serum measurement of an LH level can be used to detect ovulation, this is not commonly used as it requires a blood draw and is more expensive. Similarly, although transvaginal sonography can be used to track the growth and identify a peri-ovulatory follicle, this too is not routinely used to time intercourse because this can be expensive since it requires transvaginal sonography, and possibly multiple evaluations.

For some women, ovulation may not occur at all or can be irregular. Conditions associated with irregular or absent ovulation include PCOS, premature ovarian insufficiency, peri-menopause, pregnancy, breastfeeding, thyroid dysfunction, hyperprolactinemia, excessive stress, excessive exercise, and women who are significantly overweight or underweight. Certain medications may also affect ovulation. In women trying to conceive, ovulation prediction is a key component for intercourse timing. As a result, women who are unsure if ovulation is occurring, or may be occurring irregularly, they may benefit by consulting their Gynecologist or speaking with a fertility specialist.

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