A shortening of the luteal phase can impair pregnancy and cause miscarriage. Learn about the condition, its signs, causes and treatment options.

The menstrual cycle is often regarded as monthly menstruation, with ovulation mid-way through. However, the wonderfully fine-tuned process is a complex system involving organs, tissues, cells, hormones, proteins…the list goes on. The first half of the cycle is known as the follicular phase—the maturation of a follicle housing an oocyte and getting it ready for ovulation—while the second phase is the luteal phase and involves the preparation of the endometrium (uterine lining) either for implantation or menstruation. Luteal phase defect or deficiency, or LPD for short, is the shortening of the luteal phase, which can impair implantation and cause recurrent miscarriage. Here, we will explain luteal phase defect, the signs, causes and treatment options available to improve fertility.

What is luteal phase defect?

Luteal phase defect or luteal phase deficiency is clinically diagnosed as an abnormal luteal phase length of less than 10 days. The luteal phase is the second part of the menstrual cycle, directly after ovulation. In a “usual” 28-day cycle, the first phase of the menstrual cycle—the follicular phase—and the luteal phase are usually of equal length ~14 days. A short luteal phase is considered as 9–11 days from ovulation to menstruation, but it is good to remember that there is variation in the lenght of the follicular phase, among women and each cycle.

The luteal phase is hugely dependent on progesterone. This female sex hormone increases after ovulation and peaks 6–8 days after ovulation, preparing the endometrium (uterine lining) for implantation of a fertilized egg.

Interestingly, although it is associated with some medical conditions (see causes below), some fertile and normally menstruating women may also have the condition, but it often goes unnoticed until a woman tries to conceive.

A woman may show one or both of the following forms of LPD:

  • Clinical luteal phase defect: short luteal phase duration of less than 10 days
  • Biochemical luteal phase defect: suboptimal luteal progesterone levels of 5 ng/ml or less

What is the luteal phase of the menstrual cycle?

After ovulation, several things occur in the uterus and ovaries. Within the ovary, the corpus luteum starts to form, which is the remains of the follicle that grew and matured the oocyte that was released during ovulation. The main role of the corpus luteum at this stage is to produce large amounts of progesterone, which prepares the endometrium and uterus for implantation of the fertilized oocyte (ovum).

If the oocyte is fertilized, a blastocyst starts to form (a collection of cells that make up the early phase of an embryo). The blastocyst has to implant into the endometrium for a pregnancy to occur. This usually occurs 7 to 9 days after ovulation, and implantation can't occur after this time. So, there’s a fine-tuned timing and process for fertilization, endometrium preparation, and implantation; if these aren’t all aligned, it is difficult for pregnancy to happen.

The corpus luteum is stimulated by luteinizing hormone (LH), which is released by the brain's pituitary gland in response to the progesterone levels. If a pregnancy has occurred, another hormone, human chorionic gonadotropin (hCG), will be released. This signals the corpus luteum to continue to express progesterone, encouraging embryo growth until a placenta is formed and takes over to produce progesterone.

If a pregnancy hasn’t happened, the lack of hCG will mean the corpus luteum will be broken down, forming the corpus albicans, a scar-like structure in the ovary. This marks the end of the menstrual cycle, and both progesterone and estrogen levels drop, triggering back to the brain (hypothalamus and pituitary gland) to start the process over again.

Bringing this all back to luteal phase defect, any abnormal length of the luteal phase can affect the menstrual cycle as a whole, as well as implantation and pregnancy survival. However, it is important to point out that direct evidence to say that luteal phase defect causes infertility and recurrent pregnancy loss is lacking, and more studies are needed to determine its role in these issues.

Summary of normal luteal function

  • Luteal phase length is usually fixed at 12–14 days
  • 6–8 days after ovulation, progesterone levels peak
  • LH pulses (meaning activity releases LH in short regular bursts), which triggers the secretion of progesterone in pulses, often highest at the mid- to late-luteal phase
  • The luteal phase is dependent on the follicular phase, the hormones involved in that phase, the transition to the luteal phase, ovulation, and corpus luteum formation
  • hCG levels triggered by implantation maintain progesterone secretion; if not present, progesterone levels will decline, and a corpus albicans forms and menstruation is triggered

Causes

Specific causes for luteal phase defect are still unknown. Length of luteal phase, progesterone levels, and changes in the follicular phase of the cycle are key for producing an optimum endometrium and allowing normal embryo implantation and growth:

Length: ideally, the luteal phase should be between 12–14 days, and anything less than 10-11 days is considered a luteal phase defect.

Progesterone levels: high levels of progesterone are equally as important for implantation and maintenance of pregnancy. Therefore, any of the below issues could cause luteal phase defects:

  • Inadequate progesterone levels at specific stages of the luteal phase
  • Endometrial progesterone resistance

Low follicular phase levels: the follicular phase and luteal phase go hand in hand; if there are abnormalities in the follicular phase and its associated hormone levels, then these can affect the luteal phase, for example:

  • Low follicle-stimulating hormone (FSH) during the follicular phase
  • Low estradiol (a form of estrogen) levels during the follicular phase
  • Altered FSH/LH ratios in the follicular phase
  • Abnormal FSH and LH pulses (short bursts of regular activity to trigger release)

Conditions or diseases: that have been associated with luteal phase defect:

What are the signs and symptoms?

Women experiencing luteal phase defect have reported the following signs and symptoms:

  • recurrent first-trimester pregnancy loss
  • infertility
  • subfertility
  • short menstrual cycles (<26–28 days)
  • premenstrual spotting

Diagnosis

There are diagnostic tests that a doctor will perform to try to determine if a woman is suffering from luteal phase defect. However, precise tests and diagnostic assessments that differentiate fertile and infertile women with the condition are lacking. Your doctor may try the following methods:

Mapping menstrual cycle length: specifically the luteal phase, from the day of ovulation to the first day of menstruation, can be done by:

  • charting basal body temperature helps to determine when the LH surge occurs and estimates ovulation day
  • urinary LH surge detection kits can help map out the cycle, the LH surge triggers ovulation, so from that point to menstruation, can determine the luteal phase length

Blood tests: single or multiple blood tests during different stages of the cycle to measure serum progesterone levels. Generally, progesterone levels >3 ng/ml indicate that ovulation has occurred, but there’s no minimum serum progesterone levels that clearly define normal or fertile luteal function. Progesterone levels also fluctuate across the menstrual cycle, so a single measure doesn’t clearly indicate the state of the luteal phase; therefore, often multiple measures at different stages of the cycle may be requested.

Combination of menstrual cycle length and progesterone levels: as described in the beginning, the two forms of luteal phase defect are considered either clinical or biochemical; thus, combining the first two points could give a clearer indication of any abnormalities to the luteal phase.

Imaging: a transvaginal ultrasound may be performed to measure the lining of the endometrium at specific stages during the luteal phase.

Endometrial biopsy: a biopsy of the uterine endometrium was previously performed as a gold standard to determine abnormalities in endometrial maturation. However, it is regarded as invasive and an imprecise tool for differentiating fertile and infertile women and diagnosing luteal phase defect, due to a high variability in findings. It is unlikely your doctor will perform a biopsy to diagnose luteal phase defect, but they may request it if they suspect another issue.

Treatment

As precise diagnostic tests are lacking for luteal phase defect, precise treatment is as well. This is mainly because of the lack of clinical trials and clinical evidence to show the best ways to diagnose and treat the condition. Often, women with luteal phase defect are not aware they have it until they start trying for a baby. Thus, treatment will primarily be based on whether you are trying to conceive. Your doctor will likely:

  • Treat any underlying condition: if you already have an underlying condition or tests reveal a new condition, then the first point of call is to get that under control, for example, thyroid dysfunction, eating disorders, or obesity. By improving these conditions, the menstrual cycle may change naturally and the defect may correct itself.
  • Progesterone supplement: as progesterone is critical for the luteal phase and maintaining a pregnancy, there are options to help elevate the progesterone levels depending if you are supplementing to improve the natural menstrual cycle or for pregnancy. It can be offered orally, vaginally, or directly into the muscle. However, there is very little clinical evidence to prove that progesterone improves luteal phase defect, but studies show progesterone can reduce the miscarriage rate in women with recurrent pregnancy loss.
  • Ovarian stimulation: treatment with clomiphene citrate or gonadotropins could help stimulate the ovaries to increase the number of preovulatory follicles. The idea is that having a good follicular phase may encourage corpus luteum function and increase progesterone expression after ovulation. But again, clinical trials are lacking to confirm if ovarian stimulation can improve luteal phase defect.

Despite the lack of concrete evidence to offer clear treatment strategies for luteal phase defect, these approaches are minimally invasive and easy to administer. Therefore, it is worth trying these techniques across a few cycles to see if your cycle length changes and you are able to conceive.

Takeaway

Luteal phase defects can impact the normal menstrual cycle and affect the development of a pregnancy. You may experience short cycles or recurrent pregnancy loss. Therefore, your doctor may monitor your cycle length and test your progesterone levels during the luteal phase. Although specific treatments are lacking, supplementing with progesterone and eventually trying ovarian stimulation therapy could help improve the defect and potentially increase your chances of initiating and maintaining a pregnancy.

Contact us

If you feel that you’re being affected by luteal phase defect or any other condition that could be impacting your fertility, then contact us and arrange to meet with our compassionate team, who can guide you on your fertility journey. Reserve your spot for a free consultation today.