The luteal phase is the second half of your cycle, beginning after ovulation and ending when you get your next period. It’s something most women don’t pay much attention to unless they’re having trouble getting pregnant (a short luteal phase is associated with difficulty conceiving and early pregnancy loss). But the luteal phase is an important part of not just your fertility, but your overall health.
If you’re not being treated for infertility, it’s likely that your doctor has never asked you about your luteal phase. But this is a particularly important part of the cycle. The American College of Obstetricians and Gynecologists recently declared the menstrual cycle the “fifth vital sign”—as important to your health as blood pressure or breathing—and the luteal phase is a big part of the reason why.
What is the luteal phase, anyway?
The luteal phase is the latter part of your cycle, after the dramatic and exciting stuff has already happened. You’ve had your period, you’ve ovulated, and now your body is waiting, with bated breath, for a possible pregnancy. If you were planning a surprise party for your husband, the follicular phase would be the part where you bake a cake, gather all your friends together, and hang streamers all over the living room. The luteal phase would be the part where everyone sits quietly, the tension building as you all wait for him to get home.
After you ovulate, the corpus luteum—a structure inside the ovaries that holds a developing egg—collapses and begins to produce progesterone. Progesterone helps thicken your uterine so that if there is a fertilized egg, it has a nice, soft bed in which to implant itself. If no egg implants, the corpus luteum stops producing progesterone after about 12 – 16 days, and you shed your uterine lining in your period.
Why is the luteal phase important for women who are trying to conceive?
When we think about pregnancy, most of our minds jump straight to conception—when the sperm enters the egg. But pregnancy doesn’t really begin until the embryo implants in the uterine lining. For that to happen, your body must be making enough progesterone in order to build up a thick, healthy lining.
If your body isn’t making enough progesterone, your luteal phase will be on the short side. Anything shorter than 10 days can make it difficult to achieve pregnancy, because the uterine lining is shed before the embryo has a chance to implant.
Why is the luteal phase important for women who are not trying to conceive?
The length of the luteal phase is a good proxy for your progesterone levels. If your luteal phase is under 10 days, it’s a sign that your body isn’t making enough progesterone. And even if you aren’t trying to get pregnant, your progesterone levels matter. Adequate progesterone is crucial for maintaining healthy bones, long-term heart health, sleeping well, and feeling your best. Read more about the health benefits of progesterone.
What causes a short luteal phase?
When your body doesn’t make enough progesterone, your luteal phase will end prematurely. There are a few different reasons why you might not be producing enough progesterone:
- Thyroid disorders
- Anorexia (and milder forms of restrictive eating)
- Excessive exercise
How do you know if your luteal phase is too short?
By tracking your cycle. Count the number of days between ovulation and the start of your next period (first day of full bleeding, not spotting). Ideally, you want 12 or more days. But if your luteal phase is fewer than 10 days, you may have low progesterone.
How do you test your progesterone level?
Progesterone spikes after ovulation and continues to rise for several days. Progesterone should be tested when progesterone is highest, in the middle of the luteal phase. Typically, doctors ask women to come in for a test on day 21 of their cycles, because in the average 28 day cycle, day 21 falls in the middle of the luteal phase.
Your cycle, however, may not be the typical 28-day cycle with ovulation on day 14. Let’s say you have a 35-day cycle, with ovulation on day 23. If you get your progesterone tested on day 21, it will be very low, because you haven’t ovulated yet. But if you tested on day 29, your levels might be perfectly normal. If you know when you ovulate and how long your luteal phase typically is, you can let your doctor know the right time to test your progesterone levels.
How can you lengthen your luteal phase?
Treatment for a short luteal phase will vary depending on what’s causing it. But a few supplements have been shown to help lengthen the luteal phase:
- Vitamin C: A study in Fertility and Sterility showed that Vitamin C increases fertility in some women with short luteal phases. In the study, 25% of the women who received Vitamin C had gotten pregnant within six months compared to the placebo group in which only 11% got pregnant.
- Progesterone supplementation or cream: You can get progesterone cream over-the-counter, or in topical or suppository form from your doctor. It’s a good idea to talk with your doctor before adding progesterone supplementation to make sure you really need it. It’s also important to only use it during your luteal phase. Adding progesterone during your follicular phase could prevent ovulation.