Revised 2023


What is ovulation?

Ovulation is the release of an egg from a woman’s ovaries and is essential for getting pregnant. Ovulation is spontaneously triggered about 36-40 hours after blood levels of a hormone called luteinizing hormone (LH) rise. This is called the LH surge. Once released from the ovary, the egg is picked up by and travels down the fallopian tube where it can meet sperm to become fertilized.
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Why is ovulation important?

A problem with ovulation is a common cause for infertility. For a couple who is trying to achieve pregnancy, knowing when the woman is about to ovulate can be particularly helpful in planning when to have sex. If a woman is trying to find the reason she is not getting pregnant, it is helpful to know if she is ovulating. Having regular menstrual periods between 21 and 35 days in length accompanied by menstrual cramps is a good indication of ovulation.

There are several ways to test for ovulation, including:
  • the basal body temperature (BBT) chart,
  • urine test kits to measure LH levels,
  • blood tests to measure levels of certain hormones, and transvaginal ultrasound.


What tests are available to check for ovulation?

Blood and Urine tests

Blood tests to measure hormone levels Estradiol (a type of the hormone estrogen) is produced by the follicle as it grows, and levels go up quickly just before ovulation. If fertility medicines are being used to cause a woman to ovulate, estradiol levels are checked more often to keep an eye on the growth of the follicle, but it is not used to tell you when you might ovulate.

A rise in LH levels in the blood can predict when the follicle (sac where the egg ripens) is ripe and ready for ovulation. Because LH is released in pulses or short bursts, the LH surge is not always found by a single blood or urine test.

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Increased progesterone levels in the blood a week before the menstrual period usually indicate ovulation has occurred but cannot predict when it will occur. Urine test kits to measure luteinizing hormone (LH) levels These home test kits are available at drug stores and show changes in the level of LH in a woman’s urine.

Since LH hormone builds up in the urine, once it is detected in the urine, ovulation usually takes place within 12 to 24 hours (usually about 14 days before the start of a woman’s menstrual period).

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There is an 80% chance of detecting ovulation with 5 days of testing and a 95% chance with 10 days of testing.

For women with irregular periods, urine testing should be timed according to the earliest and latest possible dates one is expected to ovulate. Urine testing for LH surge should begin at least 2 days before the expected day of ovulation and continue until the LH surge or through day 20.

Once an LH surge is documented, it is no longer necessary to continue testing during that cycle. Occasionally, ovulation may not occur in a cycle despite an LH surge. If ovulation is not detected in 2 or more cycles in a row, there may be a problem with ovulation, and you should discuss this with your healthcare provider. Some fertility test kits check for both LH and estrogen in the urine. This does not necessarily increase your chances of pregnancy and should not be used if you are taking medicines to help you ovulate.

Transvaginal ultrasound

The egg develops within a part of the ovary called the follicle (a fluid filled sac). As the egg gets ready to ovulate the follicle grows larger. Follicle growth can be measured with ultrasound, a technique which uses sound waves to produce an image on a monitor screen using a tampon-like probe placed in the vagina. Before ovulation, the follicle is thin-walled and filled with fluid. Ovulation generally happens when the follicle measures between 1.8 and 2.5 centimeters.

For women having treatment for fertility, ultrasound may help time intercourse or insemination. In women taking fertility drugs, ultrasound may be done on several different days during the menstrual cycle to measure and monitor each follicle.

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Basal body temperature (BBT) chart

Daily measurement of basal body temperature can help determine if ovulation has occurred. However, BBT charting is only an estimate of ovulation timing and can confirm that ovulation has happened but will not predict when it might occur. Although not very helpful or accurate to time intercourse, it is an inexpensive, easy way to gather information at home.

A Final Thought

Although determining if and when ovulation is occurring might seem frustrating and time-consuming, it is often an essential step toward achieving pregnancy. It is important that women work with their healthcare providers to decide which method of ovulation detection is best for them. If these tests indicate that the woman is not ovulating, or that she has irregular cycles, treatments are available to correct the problem and increase the chances of a successful pregnancy.

Fact Sheets/Booklets

View more fact sheets and booklets written by the ASRM Patient Education Committee.
Patient Factsheet teaser

Menopausal Transition (Perimenopause): What Is It?

The menopausal transition (perimenopause) is the period that links a woman’s reproductive (childbearing) years and menopause.
Patient Factsheet teaser

Osteoporosis

Osteoporosis and osteopenia are conditions of having low bone mass (density).
Patient Factsheet teaser

Hyperprolactinemia (High Prolactin Levels)

Prolactin is a hormone produced by your pituitary gland which sits at the bottom of the brain.
Patient Factsheet teaser

Stress and infertility

It is not clear how exactly stress impacts fertility.

Resources For You

The American Society for Reproductive Medicine (ASRM) is committed to providing patients with the highest quality information about reproductive care.

Female Fertility

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SART Fertility Experts - Fertility Myths and Realities for Black Women

Black women are more likely to experience infertility and less likely to seek and receive timely treatment. Listen to the Episode
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SART Fertility Experts - Wellness and Fertility: Diet, Sleep and Exercise

Drs. Timothy Hickman and Rashmi Kudesia discuss the links between lifestyle and fertility. Listen to the Episode
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SART Fertility Experts - Preconception Counseling

This podcast episode covers the topic of preconception counseling.  Listen to the Episode
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Female Fertility Journey

If you've been trying to get pregnant for more than a year, you may have infertility. Infertility is a disease of the reproductive system that impairs one of the body's most basic functions: the conception of children.

View the Patient Journey
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Stress and infertility

It is not clear how exactly stress impacts fertility. Read the Fact Sheet
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Optimizing Natural Fertility

Before attempting pregnancy, a woman should make sure she is healthy enough for pregnancy by adopting a healthier lifestyle and taking prenatal vitamins. If she has a medical or genetic condition or risk of one, she should seek advice from a medical professional before conceiving (becoming pregnant) View the fact sheet
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Am I Ovulating?

Ovulation is the release of an egg from a woman’s ovaries and is essential for getting pregnant. View the Fact Sheet
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Abnormalities of the Female Reproductive Tract (Müllerian Anomalies)

Sometimes the uterus and fallopian tubes may not form like they should. These malformations are called müllerian anomalies or defects. Müllerian anomalies may make it difficult or impossible to become pregnant. View the Fact Sheet
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Conditions Treated with Surgery on the Fallopian Tubes and Ovaries

Surgery can be used to treat problems with the ovaries or fallopian tubes, such as cysts, endometriosis, or infections. View the Fact Sheet
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Diagnostic Testing for Infertility

An evaluation of a woman for infertility is appropriate for women who have not become pregnant after having 12 months of regular, unprotected intercourse. View the Fact Sheet
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Dilation and Curettage (D&C)

“Dilation and curettage” (D&C) is a short surgical procedure that removes tissue from your uterus (womb). You may need this procedure if you have unexplained or abnormal bleeding or if you have delivered a baby and placental tissue remains in your womb. View the Fact Sheet
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Evaluation of the Uterus

If you haven’t been able to get pregnant after trying for 6 months, some tests can be done to help find the reason. Your doctor may test your hormone levels, your partner’s sperm, and your reproductive organs (ovaries, fallopian tubes, and uterus [womb]). View the Fact Sheet
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Female Cancers, Cryopreservation, and Fertility

Yes! New technology lets your doctor remove and freeze eggs, fertilized eggs (embryos), or ovarian tissue before treating your cancer. This way, you may be able to have children after your treatment. View the Fact Sheet
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Fertility Drugs And The Risk of Multiple Births

Infertility treatments that cause multiple eggs to develop make it more likely that you will become pregnant with twins, triplets, or more. This is called multiple gestation. View the Fact Sheet
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Ovulation Detection

Ovulation, the release of an egg from its follicle in one of a woman’s two ovaries, is one of the most important factors in conceiving a child. View the fact sheet
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Weight and fertility

One of the easiest ways to determine if you are underweight or overweight is to calculate your body mass index (BMI). View the fact sheet
Patient Ed Icon

Hypothyroidism and pregnancy: what should I know?

Hypothyroidism (underactive thyroid) is when the thyroid gland produces less  thyroid hormone than it should. View the Fact Sheet
Podcast Icon

SART Fertility Experts - Endometriosis

Endometriosis is a condition that can affect many facets of a person’s life, from pelvic pain to struggles with infertility.   Listen to the Episode
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SART Fertility Experts - IVF: Cycles of Hope and Heartbreak

Does stress cause infertility or is it the other way round?  Listen to the Episode
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What is Recurrent Pregnancy Loss (RPL)?

This is a condition when a woman has 2 or more clinical pregnancy losses (miscarriages) before the pregnancies reach 20 weeks. View the fact sheet
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SART Fertility Experts - Fibroids and Fertility

Fibroids and their impact on fertility are discussed in this episode featuring Dr. Elizabeth Stewart, interviewed by host Dr. Brooke Rossi.  Listen to the Episode
Patient Ed Icon

Infertility: an Overview (booklet)

Infertility is typically defined as the inability to achieve pregnancy after one year of unprotected intercourse. View the booklet
Videos Icon

Basic Infertility Evaluation

Dr. Roger Lobo of the American Society for Reproductive Medicine discusses the various methods to evaluate infertility. Watch Video
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Fibroid Tumors

An educational video that answers patient questions about the causes, symptoms, diagnosis and management of uterine fibroids. Watch Video
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Infertility Treatments

Dr. Roger Lobo of the American Society for Reproductive Medicine discusses the various treatments for infertility. Watch Video
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Understanding Fertility

In this video series, Dr. Roger Lobo explains the basics of infertility, including causes, treatments and coping methods. Watch Video
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Surviving the Roller Coaster Emotions of Infertility Treatment

The experience of infertility is a rollercoaster of hope and disappointment. Treatment presents an opportunity for hope as well as a new set of challenges. Watch Video
Patient Ed Icon

Endometriosis (booklet)

Women with endometriosis may experience infertility, pelvic pain, or both. This booklet will describe options for diagnosing and treating pain or infertility that may be attributed to endometriosis. View the Booklet
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Causes of Female Infertility

Dr. Roger Lobo, of the American Society for Reproductive Medicine explains the causes of female infertility. Watch Video
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FAQ About Infertility

Infertility is not an inconvenience; it's a disease of the reproductive system that impairs the body's ability to perform the basic function of reproduction. Learn the facts
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Female Fertility Infographics

ASRM has prepared infographics to illustrate the subject of Female Fertility better. View the Infographics
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Ovarian Reserve Infographics

ASRM has prepared infographics to illustrate the subject of Ovarian Reserve better. View the Infographics

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