Luteal phase deficiency: what it is, why the diagnosis is debated and what to do

The menstrual cycle has two halves. The first, the follicular phase, ends with ovulation. The second, the luteal phase, runs from ovulation to the next period. After ovulation the empty follicle becomes a structure called the corpus luteum, which makes progesterone to prepare the lining of the womb for a possible pregnancy.

The ASRM committee opinion describes luteal phase deficiency as a clinical diagnosis associated with an abnormal luteal phase length of 10 days or less. It lists the proposed mechanisms as inadequate progesterone duration, inadequate progesterone levels or endometrial progesterone resistance, meaning that the lining does not respond properly to progesterone. The idea is that this could make implantation or early pregnancy less likely to succeed.

The ASRM, in its most recent committee opinion, which replaces a 2021 document of the same name, states that although progesterone is important for implantation and early embryonic development, LPD has not been proven to be an independent entity causing infertility or recurrent pregnancy loss. It adds that LPD has been described in fertile, normally menstruating women, and that controversy exists regarding the many proposed diagnostic measures and, assuming it can be diagnosed accurately, whether treatment improves outcomes.

This is a US professional society document rather than a UK guideline, and I did not find a UK national guideline devoted to LPD. The NHS pages on infertility, and NICE guidance on miscarriage, do not frame luteal phase deficiency as a standard diagnosis. They concentrate on ovulation problems, tubal and sperm factors and, for miscarriage, on investigation of recurrent loss. That absence is itself informative: UK pathways do not usually begin with a diagnosis of LPD.

The NHS says infertility in women is commonly caused by problems with ovulation, the monthly release of an egg. It lists polycystic ovary syndrome (which it also calls polyendocrine metabolic ovarian syndrome), thyroid problems, both overactive and underactive, which can prevent ovulation, and premature ovarian failure, where the ovaries stop working before the age of 40. It also lists cervical mucus problems, scarring from surgery, and medicines including long-term or high-dose NSAIDs, chemotherapy, antipsychotics and spironolactone, together with drugs such as cannabis and cocaine, as factors that can affect fertility.

In the NHS diagnosis page, tests to find the cause of infertility in women include blood tests, and the NHS says samples can be tested for progesterone to check whether you are ovulating. This is a test of ovulation, not a diagnosis of luteal phase deficiency.

Several tests have been used to look for LPD, including midluteal progesterone blood tests, basal body temperature charts, ovulation predictor kits and endometrial biopsy. The ASRM notes the controversy regarding these proposed measures. A single progesterone value is hard to interpret because progesterone is released in pulses and the right time to test depends on the timing of ovulation, which varies from cycle to cycle.

Home tracking can still be useful for a different reason. Noting cycle length, bleeding pattern and ovulation signs gives your GP information about regularity of ovulation, which the NHS treats as central to assessing fertility. Persistently short cycles, spotting before periods, very irregular periods or no periods are worth raising with a GP.

People often meet the term LPD after one or more miscarriages. In England, NICE guideline NG126 addresses progesterone in this setting. It identifies as a research recommendation the effectiveness of progestogens in women with unexplained recurrent miscarriage, noting that a randomised controlled trial of micronised vaginal progesterone in women with 3 or more first-trimester losses did not show a benefit and concluding that there is not enough evidence to support its use in unexplained recurrent miscarriage.

NICE also describes evidence from a randomised trial of a small but important benefit for live birth when vaginal micronised progesterone was given to women with early pregnancy bleeding and a history of previous miscarriage. This is specific to bleeding in early pregnancy and a prior miscarriage, and it is an NHS clinician who applies the details of the guideline. If you are pregnant with bleeding, contact your GP, early pregnancy unit or NHS 111 promptly rather than self-treating with progesterone products.

If you have been trying to conceive and are worried about the luteal phase, the useful questions are the ones the NHS pathway asks: how regular are your periods, do you ovulate, are there thyroid or other hormonal causes, are your tubes open, and what is your partner's semen analysis? These are assessed through a GP and, where appropriate, a fertility clinic. Lifestyle and medicine reviews are also part of the NHS approach.

If a clinician proposes treatment aimed at the luteal phase, such as progesterone supplements, it is reasonable to ask which guideline supports it for your situation, what the benefits and harms are and what the plan is if you do not conceive. In assisted conception cycles, progesterone support after embryo transfer is a standard, separate part of treatment and is not the same thing as treating a diagnosed LPD in a natural cycle.

Seek urgent medical help for heavy bleeding, severe one-sided lower abdominal pain, shoulder-tip pain, fainting or collapse in early pregnancy, because these may signal an ectopic pregnancy or other emergency. Call 999 or go to A&E if severe, and use NHS 111 if you are unsure.

On the NHS the route is through a GP, with referral to a fertility service when the criteria are met, and to an early pregnancy or recurrent miscarriage clinic after loss. Private fertility clinics may offer luteal phase blood tests or empirical progesterone. If you are offered tests or treatment specifically for luteal phase deficiency, ask for the evidence behind it, the cost of the whole pathway, and whether more established causes have been investigated first.