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Women's health

Luteal Phase: Its Role in the Menstrual Cycle and Fertility

The luteal phase is an important part of the menstrual cycle and if problems occur, you can have difficulty in getting or staying pregnant.

Luteal Phase: Its Role in the Menstrual Cycle and Fertility

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The luteal phase is an important part of the menstrual cycle. Although you may have never heard of it, this phase is integral in helping you get and stay pregnant.

The luteal phase starts around day 15 of your cycle. It’s responsible for thickening the lining of your uterus in preparation for pregnancy.

We spoke with naturopathic physician Amanda Alexander, ND, at Sonoran University to break down where the luteal phase fits in the menstrual cycle and why it is so important for fertility.

What is the luteal phase?

To define the luteal phase, it helps to know what its role is in the menstrual cycle. There are three phases: the follicular phase, ovulation, and the luteal phase.

The follicular phase is the first phase that begins on day one of your cycle and lasts until you ovulate. Day one of your cycle is the first day of your period when the lining of your uterus sheds and you bleed. During this phase, follicle-stimulating hormone (FSH) is produced to help grow follicles. Each of these follicles contains an egg.

About two weeks later, FSH and luteinizing hormone (LH) levels increase to make the follicles release an egg. That egg travels down the fallopian tube where it may be fertilized with sperm.

The luteal phase is the last phase of the menstrual cycle. The follicle that released an egg forms the corpus luteum which will produce the hormone progesterone. “Progesterone needs to be released at this time since progesterone helps maintain pregnancy if it occurs, says Dr. Alexander. The luteal phase is when the uterine lining becomes thicker thanks to higher levels of estrogen and progesterone to prepare for possible pregnancy.

If pregnancy happens, the follicles will produce progesterone and small amounts of estrogen during the first trimester until the placenta takes over producing progesterone, Dr. Alexander explains.

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Why is the luteal phase important for fertility?

“The early luteal phase is essentially the short receptive window during the menstrual cycle when implantation is most likely to occur. Since most eggs are only viable for fertilization for about 12 to 24 hours after ovulation,” says Dr. Alexander.

It can take a few days for the fertilized egg, known as an embryo, to get to the uterus. It can take an embryo another two to three days to implant into the uterus and begin growing and dividing, explains Dr. Alexander.

“Without adequate levels of progesterone produced during the luteal phase, it will be difficult for a pregnancy to be maintained long enough for the placenta to take over progesterone production,” says Dr. Alexander.

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How can I track the luteal phase?

According to Dr. Alexander, being aware of when you’re in the luteal phase can help you learn more about your body and use the signals it's sending about your cycle to either get pregnant or avoid pregnancy.

“There are only a few days during your cycle when you’re most likely to get pregnant. Depending on your age (and your partner's), most people have about a five- to seven-day window when pregnancy is most likely,” explains Dr. Alexander.

Some ways you can track ovulation and figure out the length of your luteal phase include basal body temperature (BBT) charting and ovulation predictor kits (OPKs). BBT charting involves taking your basal body temperature every day. A slight increase in this temperature can mean you’re ovulating. OPKs can detect a rise in LH hormone in your urine which might mean ovulation will happen in 24 to 36 hours.

woman checking her basal body temperature iStock

What problems can happen in the luteal phase?

The luteal phase typically lasts 12 to 14 days. But it can be longer or shorter depending on your menstrual cycle. Not everyone has a 28-day cycle. So it’s normal if your luteal phase lasts anywhere from 10 to 17 days.

You can have problems with the luteal phase, known as luteal phase defect (LPD). The luteal phase length is important for pregnancy and a long or short luteal phase can affect fertility and staying pregnant. In luteal phase defect, the corpus luteum breaks down earlier than usual after you ovulate, usually because of low progesterone.

“If an individual has a shortened luteal phase, it could be more difficult to achieve pregnancy since hormones begin to decrease faster, shortening the time for implantation,” says Dr. Alexander. This leads to shorter and irregular cycles, and possibly spotting. This can make it harder to get pregnant as lower levels of progesterone and estrogen signal to the uterus that there’s no baby and therefore, your period can start.

“Long luteal phases are more commonly associated with increased premenstrual syndrome (PMS) symptoms since the onset of bleeding is delayed,” says Dr. Alexander.

Keeping track of the menstrual cycle using a calendar iStock

How to support a healthy luteal phase

“Regardless of pregnancy outcomes, the luteal phase is the best time to stay hydrated and nourish the body with nutrient-dense foods to reduce inflammation,” says Dr. Alexander. This might include grass-fed beef liver, dark leafy greens, fruits rich in polyphenols and anthocyanins like pomegranates and organic cherries.

The liver stores and processes essential nutrients needed for healthy reproduction, such as vitamins A, D, E, and K, as well as minerals like iron and zinc. These nutrients are crucial for a healthy uterine lining.

According to Dr. Alexander, you should avoid processed, sugary, or fried foods and limit caffeine. "These things increase the work the liver has to do, which will make it harder for the liver to properly metabolize, or break down, hormones,” explains Dr. Alexander. The liver also removes excess hormones after they've done their job.

If you're having trouble conceiving or staying pregnant, it might have to do with your luteal phase. Working through this might mean finding a treatment to help balance your hormones. As Dr. Alexander emphasizes, it’s important to work with a healthcare provider who understands the physiology of fertility and how to treat irregular cycles, especially if you’re trying to get pregnant. Pregnancy is still possible if you have problems with the luteal phase, but it may take longer.

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This article was originally published on May 17, 2024

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Risa Kerslake is a registered nurse and freelance writer, specializing in fertility, sleep, children's health, pregnancy, and relationship topics. Her work has appeared in Parents, Discover, Romper, Vice, Shondaland, and more. She lives in the Midwest with her husband and three kids. You can find her at RisaKerslake.com

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