Luteal Phase of the Menstrual Cycle
The luteal phase of the menstrual cycle (or menses cycle) represents the second half of your menstrual cycle. It’s the final phase of a four-phase menstrual cycle. The luteal phase occurs after ovulation and before menstruation, typically lasting around 12-14 days.
The average menstrual cycle is 28-days long; however, many women experience shorter cycles (as short as 21 days) or longer cycles (up to 35 days).
The 4 Phases of the Menstrual Cycle
The menstrual cycle is defined by four distinct phases:
Menstruation: Menstruation (aka your period cycle) marks the first day of your cycle. During menstruation, you shed the lining of the uterus from the previous month’s menstrual cycle if the egg has not been fertilized.
Follicular Phase: The follicular phase of your cycle overlaps with menstruation lasting from approximately day 1 to day 13. During the follicular phase, follicles begin to form on the ovary (one of which will become an egg).
Ovulation: Around day 14-16, a follicle produced in the previous phase matures to an oocyte and is released into the fallopian tube where it will sit anywhere from 12-48 hours waiting to be fertilized.
Luteal Phase: The luteal phase lasts approximately 12-14 days immediately following ovulation. What happens during this phase depends on whether or not the egg is fertilized (more on this below). An acute rise of luteinizing hormone ("LH surge") triggers ovulation and development of the corpus luteum.
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 female body during this time.
What Happens During the Luteal Phase
During ovulation, an egg bursts from its follicle in your ovary. That ruptured follicle stays on the surface of the ovary. Over the course of the next two 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.
During this phase, the corpus luteum releases estrogen and progesterone which work to thicken the lining of the uterus in preparation for a possible pregnancy. There are two 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, it 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 pregnancy 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 fertilization and pregnancy don’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 uterine lining is what eventually causes menstruation (aka 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 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
- 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 uterine lining thickens in preparation for menstruation.
- 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 is.
When Should You Seek Medical Advice?
If you notice any of the following symptoms, it could mean something is causing an irregular menstrual cycle. It’s recommended you schedule a check-up 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
- Post-menopausal 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 Defects
If you’re suffering from an LPD, don’t panic but do see your doctor. The National Infertility Association, outlines a few hormone therapies available to treat luteal phase defects. These treatments should only be tried under close supervision from a medical professional:
- Drugs that stimulate follicle growth like Clomiphene citrate (Serophene) or human menopausal gonadotropins (hMG).
- 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, 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 labour. Manufactured forms of prostaglandins can be used to induce labour.”
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!