Luteal Phase of the Menstrual Cycle
The luteal phase of the menstrual cycle (or menses cycle) represents the last third of your menstrual cycle. It’s the final phase of a 3-phase menstrual cycle. The luteal phase occurs after ovulation and before menstruation, typically lasting around 12–14 days.
The most commonly referenced menstrual cycle is 28 days. However, the normal range for many adult women of reproductive age is 21–35 days.
Many also experience irregular menstrual cycles, which can be caused by a variety of differing factors. Tracking the menstrual cycle can be helpful in collecting information and detecting any abnormalities or deviations from your normal menstrual baseline.
Your Menstrual Cycle: The Structures and Their Phases
More popularly referred to as your period, menstruation (or menses) marks the first day of your menstrual cycle. If an egg has not been fertilized, your uterus sheds its lining from the previous month’s menstrual cycle. This is your period.
Your monthly menstrual cycle can be divided into 3 phases occurring in 2 different structures at the same time.
Structures:
- The ovary
- The uterus
Phases:
The Ovary
- Follicular phase
- Ovulation occurs
- Luteal phase
The Uterus
- Secretory
- Proliferative
- Menstruation
What Happens in the Ovary
In the ovary, the menstrual cycle is characterized by the following phases:
Follicular Phase
The follicular phase begins on the first day of your period (day 1 of your cycle) and ends with ovulation (approximately day 13–15 of a cycle of 28 days). When the follicular phase begins, follicles form on the ovary (one of which will become an egg).
Ovulation Occurs
Ovulation occurs after the follicular phase ends—around days 13–15 of your cycle in a 28-day cycle. The day ovulation occurs is distinctly defined by the act of the oocyte (immature egg) bursting through the ovarian capsule, out of the ovarian follicle, traveling through the fallopian tube, and becoming available for fertilization by sperm. The 3 days leading up to and including ovulation is when fertilization occurs.
Luteal Phase
The luteal phase lasts approximately 2 weeks after ovulation (day 17–28 in a 28-day menstrual cycle). What happens during this phase depends on whether or not the egg is fertilized. During the luteal phase, the egg begins to break down and disintegrate. If an egg isn’t fertilized before it starts to break down, it will shed with the next menses, and the cycle begins again as the body experiences a change in hormone levels. An acute rise of luteinizing hormone ("LH surge") triggers ovulation and development of the corpus luteum.
The Menstrual Cycle Timeline
During each phase, all the action happens in either the ovary or the uterus. The location and timeline of the average menstrual cycle looks something like this:
For now, we will focus specifically on the luteal phase of the menstrual cycle and discuss the importance of what happens in the human menstrual cycle during this time.
What Happens During the Luteal Phase of the Menstrual Cycle
During ovulation, an oocyte bursts from its follicle in your ovary. That ruptured follicle stays on the surface of the ovary. Over the course of the next 2 weeks, with a surge of luteinizing hormone (LH), that dominant follicle transforms into a structure known as the corpus luteum, which plays a key role in the luteal phase.
The Role of Luteinizing Hormone and Follicle Stimulating Hormone in the Menstrual Cycle
"During the luteal phase (of the menstrual cycle), luteinizing hormone and follicle stimulating hormone levels decrease," according to the Merck Manual of Diagnosis and Therapy. "The ruptured follicle closes after releasing the egg and forms a corpus luteum, which produces progesterone. During most of this phase, the estrogen level is high."
During this phase of the menstrual cycle—as luteinizing hormone and follicle stimulating hormone levels fall—estrogen and progesterone work to thicken the lining of the uterus. A thickened lining prepares it for a possible pregnancy. There are 2 possible things that can happen during the luteal phase that determine what happens next.
When the Egg Is Fertilized
If the egg is fertilized by a sperm, the fertilized egg implants in the uterine lining and the body prepares for pregnancy. The fertilized egg produces a hormone called human chorionic gonadotropin (HCG) that supports the endometrial lining and prevents it from breaking down.
HCG is also found in urine, which is what is used to detect pregnancy with at-home pregnancy tests. According to Planned Parenthood, “pregnancy tests are most accurate when you take them after you’ve already missed your period.”
In the case of fertilization, the corpus luteum maintains high progesterone levels, which also helps keep the uterine lining thick and supports the fertilized egg over the course of the following months. This will also disrupt the menstrual cycle for the duration of the pregnancy.
When the Egg Is Not Fertilized
If there isn’t a fertilized egg and pregnancy doesn't occur, the corpus luteum starts to break down and die. This typically happens around day 22 of a 28-day menstrual cycle. As the corpus luteum shrinks and dies, estrogen and progesterone levels begin to drop and the uterine lining also begins to fall away.
The collapse of the corpus luteum and uterine lining is what eventually causes menstruation (a.k.a. your period)… and the menstrual cycle begins all over again.
Luteal Phase Length: Around 14 Days
The length of the luteal phase varies from woman to woman. The average length of the luteal phase is 12 to 14 days; however, it can be as short as 11 days or as long as 17 days for some women.
If the luteal phase is longer or shorter than the average, it could mean something is happening in the body causing an imbalance of progesterone.
Luteal Phase Symptoms
If you don’t get pregnant during the luteal phase, a drop in progesterone will elicit the symptoms of premenstrual syndrome (PMS).
Some women experience severe PMS symptoms during their menstrual cycle and others may not ever experience them at all! PMS symptoms are extremely similar to the symptoms you may feel during menstruation. They include:
- Bloating and fluid retention
- Breast tenderness
- Mood related symptoms, including cravings and mood changes
- Headaches
- Trouble sleeping
Frequently Asked Questions About the Luteal Phase of Your Menstrual Cycle
Can You Get Pregnant During the Luteal Phase?
The answer to this question is both yes and no; however, the chances of getting pregnant during the luteal phase are generally quite low. You can only get pregnant if the egg is fertilized in the 12 to 24 hours following ovulation. After that, the likelihood of pregnancy decreases dramatically.
The reason for this is that the corpus luteum releases a hormone called progesterone as it breaks down. The rise in progesterone prepares the body for menstruation and causes some changes in the body that make getting pregnant extra challenging (or near impossible), including:
- The lining of the uterus thickens before menstruation begins
- Your cervical mucus dries up and creates a plug that blocks sperm from entering the uterus
- A signal is sent to the ovaries that prevent more eggs from being released
How Do You Know How Long Your Luteal Phase Is?
There are a few ways to track your menstrual cycle and detect when your luteal phase begins.
Ovulation Predictor Kits
These are kits that detect high levels of luteinizing hormone right before ovulation. 36–40 hours (on average) before ovulation, there is a brief surge in luteinizing hormone. Ovulation predictor kits (also sometimes called OPKs) detect the presence and concentration of luteinizing hormone in your urine about 12–24 hours before ovulation takes place.
Ovulation predictor kits may be especially helpful for women who are trying to conceive and want to improve their chances of getting pregnant. When used correctly, ovulation predictor kits are approximately 80% accurate in detecting ovulation with 5 days of testing and 95% accurate with 10 days of testing. Typically, testing should begin at least 2 days before the expected day of ovulation and continue until the LH surge, or through day 20.
Measure Your Basal Body Temperature
You can track your cycle by taking your basal body temperature every day at the same time (morning usually works best). Your temperature rises about half a degree right after ovulation and remains high until after your next period.
Check Your Cervical Mucus
If you’re comfortable checking your cervical mucus, you’ll notice it becomes thicker and cloudier after ovulation. This is normal variation and there’s often less of it as well.
Fertility Apps
Of course—there’s an app for that! There are many fertility apps available to help you map your cycle right from the palm of your hand.
They all use a similar algorithm to collect data, track changes in your cycle, and predict when ovulation occurs and when you should expect your next period.
Keep in mind that fertility apps are not an exact science and don’t replace regular check-ins with your doctor. They also typically work best for women who have a regular menstrual flow.
When Should You Seek Medical Advice?
If you notice any of the following symptoms during your reproductive life, it could mean something is causing an irregular menstrual cycle. It’s recommended you schedule a checkup with your doctor and seek medical advice if you experience:
- Heavy periods with large, quarter-sized clots
- Irregular periods
- Spotting between periods along with abdominal pain or cramping
- Pain or a burning sensation when you pee
- Unusual vaginal discharge and/or redness and itchiness
Always seek medical advice in the following situations:
- If you think you’re pregnant
- If you experience inconsistent spotting on a regular basis.
- Bleeding or spotting begins after unprotected sex
- Postmenopausal vaginal bleeding
Luteal Phase Irregularities and Treatments
Slight fluctuations in the length of the luteal phase are normal; however, there are certain situations that lead to irregularities in the luteal phase. This is typically caused by irregular progesterone levels that lead to problems with the development of the uterine lining.
A short luteal phase occurs when the body isn’t producing enough progesterone, caused by a condition called luteal phase defect (LPD). Insufficient progesterone prevents the uterine lining from developing properly and, therefore, impacts your ability to get (and stay) pregnant. If your luteal phase is shorter than 11 days, it’s advised you seek medical advice.
Some other causes of a short luteal phase include:
- Hyper or hypothyroidism
- Eating disorders like anorexia
- Excessive exercise
- Extreme stress
- Age and weight
Hormone Therapies for Luteal Phase Defect
If you’re suffering from a luteal phase defect, don’t panic but do see your doctor. Resolve, The National Infertility Association, outlines a few hormone therapies available to treat luteal phase defects. These treatments for luteal phase deficiency should only be tried under close supervision from a medical professional:
- Drugs that stimulate follicle growth like clomiphene citrate (serophene) or human menopausal gonadotropins (HMGs)
- Human chorionic gonadotropin (HCG) can be taken to increase progesterone secretion from the corpus luteum
- Progesterone can be taken orally, injected, or taken as a vaginal suppository
If your luteal phase lasts much longer than 17 days, it could be a sign of a hormone imbalance caused by something like polycystic ovarian syndrome (PCOS).
A Note on the Secretory Phase
While the luteal phase elicits a flurry of activity in and around the ovaries during the menstrual cycle, there is another phase happening concurrently in the uterus. It’s called the secretory phase.
During the secretory phase, the progesterone released by the corpus luteum in the ovaries stimulates the endometrium to secrete substances called prostaglandins (PGs).
The Society for Endocrinology states: “Prostaglandins are known to regulate the female reproductive system, and are involved in the control of ovulation, the menstrual cycle and the induction of labor. Manufactured forms of prostaglandins can be used to induce labor.”
If the egg is fertilized, PG production is inhibited so as not to disrupt the early stages of pregnancy. If fertilization doesn’t occur, the PGs help the uterine lining break down and the body prepares to shed it during menstruation—and the cycle begins all over again!
Written by Jane Flanagan — Updated on March 1, 2022.