In a recent installment of our “FAM Basics” series, we discussed the hormone progesterone, the “yin” to estrogen’s “yang.” As we shared, the release of progesterone from the corpus luteum (a small cyst produced on the ovary as a result of ovulation) after ovulation does two things: 1) It helps balance the effects that estrogen had in the first half of the cycle known as the follicular phase, and 2) It gives the second half of the cycle its name–the luteal phase.
In this article, we will quickly review the two phases of the hormonal cycle, and then explore the luteal phase more. We’ll specifically look at what normally happens during the luteal phase, plus how hormonal imbalances can impact it.
The follicle comes first
The hormonal cycle consists of two phases: the follicular phase, which begins with menstruation and continues through ovulation, and the luteal phase, which begins after ovulation and ends with the next period. You can remember the order of the phases by remembering that “the follicle comes first.”
During the follicular phase, where the action occurs in the ovaries, we see a rise in both estrogen and progesterone. You can see in the picture below that the rise in progesterone is slower than the rise in estrogen. These hormonal changes set the physical process leading up to ovulation (i.e., release of an egg from an ovary) in motion. Each egg is contained inside a follicle, and ovulation occurs when one egg is released from a follicle, known as the dominant follicle (many follicles are stimulated to mature but only one, and occasionally more as in fraternal twins, is dominant).
A woman charting her cycle using a fertility awareness method (FAM) will know she’s likely approaching ovulation when she observes clear, stretchy cervical mucus, often described as egg-white cervical mucus, and/or when she feels a lubricative sensation. Ovulation also triggers a rise in basal body temperature (BBT), or the temperature of the body when it is at complete rest. Basal body temperature remains elevated until the next menstrual period (or longer, if pregnancy occurs). Daily BBT readings are part of the symptothermal methods of fertility awareness.
What happens during the luteal phase?
After ovulation, the luteal phase begins. The now-empty follicle turns into a free-floating gland called the corpus luteum, which produces progesterone during the luteal phase, or, if fertilization occurs, for the first three months of pregnancy. In a normal luteal phase, progesterone first increases quickly and then tapers by the end of the cycle unless fertilization occurs, in which case progesterone remains at a high level to support the pregnancy.
Progesterone plays several roles during the luteal phase. It causes the cervix to stop secreting fertile mucus and to start secreting gestagenic mucus, a dense mucus that effectively seals the cervix to keep sperm and other microorganisms from entering the body, in order to protect the pregnancy (should one occur). A woman who is charting her cervical mucus biomarker as part of a FAM will no longer see or feel the clear, stretchy, lubricative fertile mucus and will begin feeling a dry sensation instead. This type of infertile cervical mucus may appear in small amounts as thick, sticky discharge, or may not be observable at all. Gestagenic mucus dissolves at the end of the cycle.
Progesterone also causes the lining of the uterus, the endometrium, to thicken. If pregnancy occurs, this thicker endometrium supports the implantation of a fertilized egg. If pregnancy doesn’t occur, the lining is shed in menstruation.
What is a healthy luteal phase length?
According to the FEMM method of fertility awareness (which, full disclosure, I teach!) a healthy luteal phase lasts about nine to 18 days, with an average of 12 days. Each woman’s luteal phase length should be consistent from cycle to cycle, with an occasional normal variation of one day longer or shorter. A normal luteal phase length is a good indicator that ovulation occurred and that hormones are at healthy levels. One requirement for a healthy luteal phase is a healthy corpus luteum, which can be affected by inflammation, thyroid disease, or insulin issues, according to Period Repair Manual, a book by Lara Briden, ND.
A short luteal phase, also known as a deficient luteal phase or luteal phase defect, indicates that the hormones in the follicular phase likely did not reach sufficient levels. Stress can also cause a short luteal phase. A complete lack of a luteal phase can indicate that ovulation didn’t occur at all.
A deficient luteal phase results in low progesterone and can result in infertility or early pregnancy loss; after all, the endometrium needs enough time to thicken to support implantation, and sufficient levels of progesterone are required for both implantation and maintenance of a healthy pregnancy. A deficient luteal phase also can be a sign of another problem that can cause infertility, such as polycystic ovary syndrome (PCOS). Low progesterone can cause other problems, which we discussed in our FAM Basics article on progesterone.
As a result of the natural drop in progesterone that occurs at the end of the luteal phase, experiencing some mild breast tenderness, bloating, cramps, headache, fatigue, insomnia, and irritability during the couple of days leading up to menstruation is normal. However, more severe symptoms that significantly disrupt a woman’s life are not normal, and might be premenstrual syndrome (PMS) or premenstrual dysphoric disorder (PMDD), which can be caused by low progesterone during the luteal phase.
Signs of a deficient luteal phase, and how to get help for it
You might have a deficient luteal phase if you have tail-end brown bleeding (brown bleeding or spotting at the end of your normal red menstrual flow), more than two days of premenstrual spotting (red or brown), a short luteal phase (less than nine days), or a poor, inconsistent, or lack of basal body temperature rise. If you notice a pattern of any or all of these symptoms–all of which can be seen and recorded in a menstrual chart–it’s a good idea to bring it up with your provider.
Many medical providers test progesterone via a blood sample on day 21 of the cycle to try to diagnose a luteal phase problem. This one-size-fits-all approach is flawed because it’s not based on when an individual woman ovulated during that particular cycle. Restorative reproductive health providers use a different approach, in which the woman identifies her peak day (the day she most likely ovulated, or very close to it) based on her charting, and has her progesterone tested on multiple days during her luteal phase to observe whether her progesterone is rising and falling appropriately.
If your medical provider is testing your progesterone before you’ve seen any signs of ovulation (meaning that you’re likely still in the first half of your cycle) or only on day 21 of your cycle, it may be time to find a new provider. NaPro, NeoFertility, and FEMM-trained medical providers, for example, are well equipped to evaluate and treat a deficient luteal phase.
The importance of charting
Without knowing how to chart her cycle, a woman is unable to identify her luteal phase and therefore may not be able to understand if something is off in this important part of her cycle. The health of a woman’s luteal phase is especially critical information for couples trying to conceive, but it is also an important overall indicator of health for every woman (no matter what her fertility goals may be). Working with an instructor to learn to chart your cycle is a key first step in understanding—and improving—your health.
Additional Reading:
FAM Basics: What is the Follicular Phase of the Menstrual Cycle?
Cycle Syncing: How to Hack the Natural Hormonal Shifts of Your Cycle
Thyroid Dysfunctions and Your Fertility: How FAMs Can Help You Get to the Bottom of Hypothyroidism
