Women who have their periods regularly and have not experienced any clear issues with their cycle, might not expect to run into problems getting pregnant or having miscarriages.

Unfortunately, we know all too well that this is not always the case. If you are having trouble with pregnancy despite regular periods, something called luteal phase defects (LPD) might be the cause.

This condition affects the levels of progesterone that women produce during their menstrual cycle. But what exactly is LPD and how does it affect fertility?

What does a normal cycle look like?

A normal menstrual cycle begins with the Follicular Phase on the first day of bleeding and lasts about two weeks. During this phase, a follicle-stimulating hormone (FSH) is released to help the eggs in the ovaries develop.

Estrogen is also produced during this phase so the uterine lining can also develop, essentially preparing your body to house an egg.

Once the Follicular Phase is completed, you will enter the Ovulation phase. Ovulation occurs when you have produced the maximum amount of estrogen your body needs to release the most mature egg.

The ovulation phase usually lasts between 12-24 hours, but you can still become pregnant a few days before or after ovulation.

Once the egg is released during ovulation, the follicles begin to release a hormone called progesterone. Progesterone is very important for the fertilized egg to successfully implant in the uterus and begin to grow.

This is also known as the Luteal Phase, which usually lasts between 12-16 days.

If the body has produced an adequate amount of cervical fluid during the first three phases, and the sperm is successfully carried to the fallopian tubes, the egg should become fertilized, also known as the moment of conception!

If the egg is not fertilized, the cycle will begin again.

What is luteal phase deficiency?

Luteal phase deficiency (LPD) is a condition in which during the Luteal Phase, women do not produce enough progesterone for the egg to either implant or for an embryo to grow.

LPD was first recognized in 1949 as a potential cause of infertility. Although more than 70 years have since passed, a full understanding of the cause and diagnosis of LPD has still not been reached.

In fact, as of 2012, the American Society for Reproductive Medicine states that a direct link between LPD and infertility has yet to be proven.

However, other research claims to reveal information that does link LPD and infertility.

Signs of LPD

Because the signs of LPD are so subtle, it can be hard to diagnose. Many women may not even take note of the signs until they experience issues with pregnancy.

Women with LPD have been found to experience a shortened Luteal Phase of less than 9 days. But other research shows that up to 5% of healthy fertile women also experience short luteal phases without experiencing fertility loss.

One study looked at five women who had experienced multiple miscarriages who were otherwise healthy. All five patients were found to experience spotting before their periods on a regular basis. All five women also had below-average progesterone levels from the 6th day of their luteal phases.

Abnormalities in hormone levels may be able to point to LPD, but the exact cause of hormone imbalances can also be difficult to pinpoint.

What causes LPD?

While the exact causes of LPD are still unknown, and additional data is needed to present exact numbers, LPD is considered very common. One study found that out of 463 cycles, there were 41 cycles (8.9%) with clinical LPD.

Any health condition that affects hormone levels in your body could be an underlying cause of LPD.

Some of the main conditions that could affect hormone production in women are:

• Polycystic ovarian syndrome (PCOS)
• Endometriosis: Conditions like PCOS and endometriosis affect the menstrual cycle and normal development of both the uterine lining and hormones during the luteal phase.

• Thyroid dysfunction: thyroid issues can lead to the disruption of certain hormone production and an increase of thyrotropin hormones, which can cause imbalances.

• Excessive exercise
• Stress: Excessive exercise and stress can also disrupt normal hormone production and cause irregular menstrual cycles.

• Obesity: Has been linked to fertility and pregnancy loss due to issues with progesterone production.
• Eating disorders: Women with eating disorders have also been shown to experience a reduction in the hormones produced during the luteal phase.

• Aging: Women of later reproductive age also experience decreased progesterone production during the luteal phase.

Because of the difficulties in diagnosing LPD, there are still challenges in making direct connections between these conditions and LPD.

But by determining whether or not a woman is experiencing anything else that could affect her hormone levels, doctors can try to come up with the best course of treatment.

Diagnostic tests for LPD

While there are some tests to try and diagnose LPD, there is no real reliable way to differentiate between fertile and infertile women.

The least invasive test doctors have used to try and diagnose LPD is measuring the menstrual cycle. However, there are a few issues with this test.

For one, studies have found that 13% of menstrual cycles are associated with a luteal phase that is 10 days or less. Not all women with a short luteal cycle experience issues with fertility.

Another issue is that the luteal phase can only be measured in cycles that do not result in pregnancy, making it hard to know what the exact length of the luteal phase is for women who become pregnant.

The second diagnostic test doctors have tried for LPD is measuring progesterone levels. This test also has its drawbacks because progesterone levels oscillate between 5 and 40 ng/mL over such a short period of time that a single random measurement does not reveal very much.

Taking a sample every day of the luteal phase is not exactly practical, so some doctors have determined that taking three samples should be adequate.

Another potential problem with measuring hormone levels is that progesterone production varies even in healthy fertile women. Overall, this test has not been clinically validated.

In the past, some doctors performed endometrial biopsies, in which a small biopsy of the uterine wall was performed. Because this procedure is rather invasive and never yielded any valuable results, it is also considered clinically invalid for diagnosing LPD.

Treatment for LPD

It should come as no surprise that due to the difficulties with diagnosis, data on treatments for LPD is lacking. The good news is, as we mentioned above, not every woman with LPD has difficulty conceiving.

In the case that a woman with potential LPD and an underlying condition is experiencing fertility issues, treating the underlying condition, if possible, may solve the issue.

If there is no clear cause behind the potential LPD, taking progesterone supplements, paired with fertility treatments like IVF is the general course of treatment. Fertility treatments are an important piece of the treatment plan since there is no evidence that taking progesterone supplements can help to improve the natural menstrual cycle.

There is also conflicting evidence about progesterone supplements lowering the chance of miscarriage. While one study supports this hypothesis, there are others that do not think the data is strong enough to make a clear correlation.

It is unfortunate that in the 70-plus years since LPD was discovered, there is still so little understood about the condition. Hopefully, in the future, further research will help develop more accurate tests to understand whether or not LPD is directly linked to infertility so that treatment can improve.