What a Short Menstrual Cycle Says About Your Pregnancy Odds

Having a menstrual cycle that's on the shorter side is quite common. The average cycle length is 28 days, but research has found that 91% of people have a cycle length between 21 and 35 days. That's a huge range! Still, if your cycle is short or irregular, you might be concerned about how this could impact your fertility.

Although shorter cycles don't always impact fertility, having concerns about a 24-, 25-, or 26-day cycle is understandable. We reached out to experts to explain how short menstrual cycles could affect fertility, how to address any issues, and how to optimize your chances of conception if you have a shorter cycle.

What Is a Menstrual Cycle?

The menstrual cycle is a natural process that involves hormonal shifts and changes in the uterus and ovaries. It's what makes pregnancy possible. Menstruation is the part of the cycle when your uterine lining sheds (commonly known as a period).

Each cycle, your uterus builds up this lining—composed of blood and uterine tissue—in preparation for a possible pregnancy. But if pregnancy doesn't occur, you shed the lining, which results in you getting your period.

While the average cycle is 28 days, your cycle is considered "normal" if it falls between 24 to 38 days. So, while on the short end, it's still within the typical range to have a 24-, 25-, or 26-day cycle. Menstrual cycles are usually divided into four parts:

• Menstrual phase: You have your period and bleed, usually for about three to five days.
• Follicular phase: This phase starts with the menstrual cycle (so it overlaps with the menstrual phase) and ends with ovulation. It's during this phase that your body gets ready to release an egg. On average, the follicular phase lasts 17 days.
• Ovulatory phase: This is when your body releases an egg, usually about 14 days before your next cycle.
• Luteal phase: In this phase, your body prepares the uterus for pregnancy; this phase lasts on average about 12 days.

It's normal for menstrual cycles to vary from one person to another. But having very short, very long, or unusually erratic cycles can signal fertility concerns, says Jenna Turocy, MD, an OB-GYN and reproductive endocrinologist at Columbia University Fertility Center.

"[The] menstrual cycle reflects a person's overall health status and should be thought of as a key vital sign," she explains. "Variations in the length of the menstrual cycle may indicate hormonal imbalances and whether or not ovulation is occurring in a predictable manner."

How Does a Short Menstrual Cycle Affect Fertility?

It's important to note that having a short cycle in and of itself doesn't mean you will have trouble getting pregnant. "Some variation in cycle length can be normal," explains Michael Zinger MD, a reproductive endocrinologist at RMA Long Island IVF. However, if you usually have a cycle that's less than 24 or 25 days, something may be amiss.

There are two main things that can go wrong in a shorter cycle that can impact fertility, explains Dr. Zinger. First, if your cycle is short, it may indicate that you are having trouble ovulating or that ovulation isn't occurring. A short menstrual cycle can also indicate that your luteal phase (the period between ovulation and menstruation, when your uterine lining is building) isn't long enough.

So, how do you know whether there may be an issue? "The easiest way to tell which of the phases is shortened is to track ovulation, which can usually be done with over-the-counter urine tests," says Dr. Zinger. "Most urine tests for ovulation will turn positive a day or two before ovulation."

You can then compare your test results to an online ovulation calculator. If ovulation seems to be occurring earlier or later than the calculator estimate, it can help pinpoint whether it's your follicular (earlier) or luteal (later) phase that is shorter than expected.

A shorter follicular phase isn't always a problem as long as you are ovulating. But if you are older and experiencing a shorter follicular phase, you should talk to your health care provider about it. "If the follicular phase has become shorter with age, it may be an indication that the egg supply is decreasing," Dr. Zinger says.

Alternatively, if ovulation occurs where expected, but your next period occurs less than 10 days later, you may have a short luteal phase. According to the American Society for Reproductive Medicine (ASRM), luteal phases that are less than 10 days might indicate luteal phase deficiency (LPD), which can impact fertility. Even if you ovulate, if your body can't secrete the hormones (primarily progesterone) to support pregnancy during the luteal phase and build up a proper uterine lining, pregnancy may not be successful.

If luteal phase defects are suspected, your health care provider will carry out certain tests to figure out what is causing this issue, says Dr. Zinger. "A doctor can check for hormone conditions that are causing luteal phase defects, such as a thyroid disorder or over-production of prolactin hormone," he explains. "Fixing these underlying conditions with the correct medication would then also correct the luteal phase defect."

Increasing Your Chances of Conception With a Short Cycle

If you are concerned that your 24-, 25-, or 26-day (or shorter) cycle is impacting your fertility, there are two main areas to focus on: identifying and treating any medical conditions and becoming more aware of the signs of ovulation.

Treat any underlying medical conditions

There are a few medical issues that may be related to short menstrual cycles and that can impact fertility, says Dr. Turocy. "If you are concerned, and your menstrual cycle is short, work with your doctor to try to determine the cause," she recommends.

Short cycles are considered "irregular" if they are shorter than 24 days. Causes of irregular periods include:

• Thyroid dysfunction
• High prolactin
• Short luteal phase
• Eating disorders
• Certain medications
• Polycystic ovary syndrome (PCOS)
• Primary ovary insufficiency (when ovaries stop working normally before 40)
• Pelvic inflammatory disease (PID)
• Stress
• Uncontrolled diabetes
• Obesity

For each of these conditions, there are effective treatment options and hope for future conception. For example, thyroid issues can be addressed by thyroid medications to help your body reach appropriate levels. Likewise, high levels of prolactin can be remedied with medication and addressing any physiological issues that may be causing the problem.

Luteal phase defect is usually addressed with hormonal medication or medication to stimulate ovulation. Finally, if you are dealing with decreased ovarian reserve, there are options to maximize your chances of conceiving, such as using in vitro fertilization (IVF), freezing your eggs, or using a donor egg.

Learn the signs of ovulation

If you are ovulating, timing baby-making sex or insemination around ovulation can increase your chances of conceiving. So learning the signs of ovulation is a smart idea—whether you are having fertility issues or not.

"Knowing when you ovulate can help you figure out when you're most fertile and the best time to have sex," says Dr. Turocy. "I recommend having sex every one to two days during your fertile window (6 days before ovulation)."

How can you tell when you are ovulating? Thankfully, there are actually quite a few signs:

• More copious, slippery cervical mucus (with a raw egg-white consistency)
• Increased sex drive
• Bloating
• Pelvic pain, usually on one side
• Spotting or light bleeding

Other methods include over-the-counter ovulation detection kits and basal body temperature readings. Body temperature rises slightly after ovulation, and tracking your basal body temperature first thing in the morning (before you get up) can help you get more in tune with when you are ovulating and what the signs look like in your body.