What is the luteal phase of your menstrual cycle and how does it affect you?

Turns out it's pretty important for baby-making

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You might have had your period for around half your life (or longer), but there's still stuff you might not have known about it. Like the luteal phase, for example. The luteal phase is the time after you ovulate, but before you get your period - essentially, the 'second half' of your menstrual cycle. Biologically, it's when your body is preparing for you to put a bun in that oven (whether you're actually planning to or not - Mother Nature's not a mind reader, you know…)

Generally, a luteal phase will last about 12-14 days, and even if you're not trying to get pregnant, it can still give you some important indications about your health. Here's everything you need to know about your luteal phase, from figuring out when it is to what it can tell you about your body…

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. "A normal adult's menstrual cycle is between 24 to 38 days long. The first half of your menstrual cycle (the follicular phase) is more flexible, and can last anywhere from 14 to 21 days. The second half of the menstrual cycle (the luteal phase) is more rigid.

"To be sure of how long your luteal phase, you need to determine which day you are ovulating (you can do this using LH ovulation urine test, or with measures involving cervical fluid and basal body temperature tracking) and then track which day you start your period. 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 them an indicator of when your uterine lining is thick, healthy, and ready to support a baby. It can also flag up potential problems with your fertility - such as a luteal phase defect (more on that later).

But even if you're not trying to get pregnant, understanding your luteal phase and your menstrual cycle as a whole can still be useful. "During your luteal phase, progesterone is the prevailing sex hormone," explains Nicole. "These times of high progesterone can have effects on your whole body."

"For instance, progesterone causes a rise in your core body temperature by ~0.4 degrees Celsius. This 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."

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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," she details. "Scheduling to quit cigarette smoking during your luteal phase, for example, may make you less likely to give in to your cravings."

What is a luteal phase defect?

Okay, so this is where things get a bit more scientific, but Nicole breaks it down: "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," she says. "The 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 is referring 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. If this is the case with you, you may find that your body cannot maintain the endometrial lining, so that 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," she 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," Nicole advises. "This could potentially include hypothalamic dysfunction, thyroid disorders, ovulation dysfunction, or hyperprolactinemia."

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.

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