EYNTK about the luteal phase of your menstrual cycle

young woman lying on bed with hot water bottle on tummy
The luteal phase of your menstrual cycle explainedIAN HOOTON/SCIENCE PHOTO LIBRARY - Getty Images

Just when you think you've figured out your entire menstrual cycle, there's always something new and interesting to learn. Like did you know your cycle is made up of four stages, each one serving a different function? This includes the more well-known menstrual phase, along with the follicular phase, ovulation, and the luteal phase (the one we're here to talk about).

In a nutshell, it's when your body prepares itself for the possibility of pregnancy. Starting straight after you ovulate, it lasts up until you start your next period and is essentially the 'second half' of your menstrual cycle.

Your luteal phase can last around 14 days, and while it plays a pretty big part in pregnancy, it has other functions too – and can give you some important indications about your health. Which is why it's worth reading into it and getting to know the facts.

Still curious? Here's everything you need to know about your luteal phase, from figuring out when it is in your cycle to what it can tell you about your body...

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What is the luteal phase?

As briefly mentioned above, your menstrual cycle comprises of four stages and the luteal stage is one of those four. It is the stage that follows ovulation and sees your body prep itself for the possibility of a pregnancy.

What are the luteal phase symptoms?

If you're not pregnant during this phase, you might experience symptoms of premenstrual syndrome (PMS) – joy! These could be anything from bloating and tender breasts, to mood changes, headaches and food cravings – a sure sign you're about to start menstruating.

How can you work out how long your luteal phase is?

"Everyone's menstrual cycle is different and unique," says Nicole Telfer, Scientific Researcher at Clue. "The length of a menstrual cycle varies among women and people who menstruate, but the average is around 28 days, according to the NHS. Regular cycles that are longer or shorter than this (from 23 to 35) are also considered normal."

Telfer adds that the first half of your menstrual cycle (the follicular phase) is more flexible, and can last anywhere from 14 to 21 days and the "second half of the menstrual cycle (the luteal phase) is more rigid".

"To be sure of how long your luteal phase is, you need to determine which day you are ovulating and then track which day you start your period," she continues. "The time between ovulation and the start of your period is your luteal phase."

Why is the luteal phase important?

For obvious reasons, the luteal phase is pretty crucial for anyone who's trying to conceive, as it gives an indicator of when your uterine lining is thick, healthy, and ready for a fertilised egg. It can also flag up potential problems with your fertility – such as a luteal phase defect (more on that later).

Telfer explains that "during your luteal phase, progesterone is the prevailing sex hormone," and these times of "high progesterone can have effects on your whole body." For example, she shares that progesterone causes a rise in your core body temperature by ~0.4 degrees Celsius which can "influence your ability to perform physical endurance and performance activities."

"Be sure to give yourself a break if you find you can't make the training targets that you were hitting the week before," she adds.

It's not all bad news though – your cycle phase may also have a positive impact, in particular on your ability to break bad habits at the time. "High levels of progesterone during the luteal phase may help increase a person's ability to exert more 'cognitive control' by enforcing good decision-making skills, instead of falling prey to cravings," says Telfer. "Scheduling to quit cigarette smoking during your luteal phase, for example, may make you less likely to give in to your cravings."

a woman in a swimsuit holding a pregnancy test
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What is a luteal phase defect?

Okay, so this is where things get a bit more scientific, but thankfully, Telfer is here to break it down. She explains that "once an egg is released from an ovary at ovulation, the cells that were previously supporting the egg [the ovarian follicle] change function and turn into the corpus luteum."

"The [very fancy sounding] corpus luteum produces progesterone. Progesterone is the hormone responsible for maintaining your endometrial lining so that a fertilised egg can implant and grow. A luteal phase defect refers to a fault in the corpus luteum's ability to produce enough progesterone."

In basic terms, a luteal phase defect is when this corpus luteum does not produce enough progesterone, or when the second phase of a cycle after ovulation isn't supported well.

If this is the case with you, you may find that your body cannot maintain the endometrial lining, so it begins to degenerate early, shortening your luteal phase and bringing on an earlier onset of a menstrual period. "At the other end of the spectrum, the length of the luteal phase may be normal, but the overall output of progesterone could be low, which could result in an under-supported endometrium," Telfer adds.

"With either of these manifestations of luteal phase defects, some researchers theorise that there could be a negative impact on fertility through increased chances of early miscarriages. The topic of whether luteal phase defects are actually clinically relevant and if they have an impact on fertility is still a very controversial topic. For now, more research is needed in this area."

How can you make your luteal phase longer?

"If there is an underlying illness or dysfunction that is causing consistently shortened luteal phases or chronically low levels of progesterone, then it is important to address that first," Telfer advises. She says that this could potentially include hypothalamic dysfunction (a problem with the hypothalamus, a part of the brain), thyroid disorders, ovulation dysfunction, or hyperprolactinemia (where you have higher-than-normal levels of the hormone prolactin in the blood).

However, it's important to keep in mind that many people with normal menstrual cycles can experience variation in the length of their luteal phase, with some shortened luteal phases. This is not a sign of disease and is considered normal - but if you'd still like a second opinion to provide you with peace of mind, it's always best to check in with your doctor if you're unsure about anything.

For more information on the luteal phase, visit this NHS Foundation Trust website page.

This article is not intended to be a substitute for professional medical advice or diagnosis. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

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