Irregular Periods and Getting Pregnant: What to Know

✨

Irregular ≠ Infertile

Many women with irregular periods ovulate at least some of the time and can conceive naturally. The key is accurately identifying when you ovulate—not relying on calendar predictions that won't work for you.

If your cycle is unpredictable, you know the frustration: apps are useless, and the "day 14" ovulation rule certainly doesn't apply. But irregular periods don't necessarily mean you can't get pregnant—they mean you need to track differently.

Let's understand what causes irregular cycles, how they affect fertility, and how to find your fertile window when your body won't give you regular signals.

What Counts as "Irregular"?

Cycle Length Definitions

Regular cycles 21-35 days, with variation of 7 days or less between your shortest and longest cycles

Irregular cycles Cycles that vary by more than 7-9 days in length from month to month (e.g., 25 days one month, 40 days the next)

Oligomenorrhea Cycles consistently longer than 35 days, or fewer than 8-9 periods per year

Amenorrhea Absence of periods for 3+ months (or 6+ months if previously irregular)

Note that "regular" includes a range—cycles anywhere from 21 to 35 days are normal if they're consistent for you. A 32-day cycle is just as normal as a 28-day cycle.

Common Causes of Irregular Periods

Understanding why your periods are irregular can guide treatment:

PCOS (Polycystic Ovary Syndrome) Very Common

The most common cause of irregular periods in reproductive-age women. Hormonal imbalances (high androgens, often insulin resistance) disrupt ovulation, causing long, unpredictable cycles or absent periods.

Other signs: Acne, excess hair growth, weight gain, difficulty losing weight

Stress and Lifestyle Factors Very Common

High stress, significant weight changes, excessive exercise, or disrupted sleep can suppress the hormonal signals (GnRH) that trigger ovulation. Often temporary if the underlying cause is addressed.

Other signs: High stress levels, recent weight loss/gain, intense athletic training

Thyroid Disorders Common

Both hypothyroidism (underactive) and hyperthyroidism (overactive) can disrupt menstrual cycles. The thyroid interacts closely with reproductive hormones. Often easily treatable with medication.

Other signs: Fatigue, weight changes, hair loss, temperature sensitivity, anxiety or depression

Hyperprolactinemia Common

Elevated prolactin (the hormone that stimulates milk production) suppresses ovulation. Can be caused by medications, pituitary tumors, or stress. Usually treatable.

Other signs: Milky nipple discharge (galactorrhea), reduced libido

Primary Ovarian Insufficiency (POI) Less Common

Premature decline in ovarian function before age 40, causing irregular or absent periods. Different from early menopause—ovulation may still occur intermittently.

Other signs: Hot flashes, vaginal dryness, symptoms similar to menopause

Hypothalamic Amenorrhea Less Common

The brain's hypothalamus stops signaling for ovulation, usually due to low body weight, extreme exercise, or severe stress. Reversible when the underlying cause is addressed.

Other signs: Low BMI, high exercise levels, restrictive eating patterns

💡 Get Tested

If your periods are irregular, basic blood work can help identify the cause: TSH (thyroid), prolactin, FSH, LH, AMH, and possibly testosterone and DHEA-S (for PCOS). Knowing the cause helps determine the right treatment.

How Irregular Cycles Affect Fertility

The fertility impact depends on why cycles are irregular:

If you're still ovulating (just unpredictably): You can absolutely get pregnant—you just need to catch the right days. Tracking is harder but not impossible. Each cycle you ovulate, you have a chance.

If you're ovulating infrequently: Fewer ovulations = fewer chances per year, so it may take longer. Treatment to induce ovulation can help.

If you're not ovulating at all: You cannot conceive without ovulation. The good news: most causes of anovulation are treatable, and once ovulation is restored, pregnancy rates are often similar to women with regular cycles.

Tracking Ovulation with Irregular Cycles

Standard calendar methods won't work for you. Here's how to track when your cycle is unpredictable:

🌡️

BBT Charting

Track basal body temperature daily. The temperature rise after ovulation confirms it happened, even if you can't predict when. Over time, you may spot patterns.

✓ Best for confirming ovulation occurred

💧

Cervical Mucus

Watch for egg-white cervical mucus (EWCM)—it appears before ovulation regardless of cycle length. When you see it, ovulation is likely within 1-3 days.

✓ Best for predicting ovulation is coming

📊

OPKs (with caveats)

Can work but may require testing for many days. With PCOS, you may get false positives due to elevated baseline LH. Use alongside other methods.

📲

Wearable Monitors

Devices like Tempdrop or Ava track multiple parameters and may help identify patterns even with irregular cycles. More data = better pattern recognition.

The best strategy: Combine methods. Watch for cervical mucus changes (predictive), confirm with BBT (confirmation), and have sex when you see fertile signs regardless of what day of your cycle it is.

🌡️

Great for Irregular Cycles

Tempdrop Wearable BBT Sensor

Tracks temperature while you sleep—no waking at the same time required. The algorithm learns your patterns and works well even with irregular sleep. Great for women with variable schedules or irregular cycles.

Check Price →

What If You're Not Ovulating?

If tracking shows you're not ovulating (no temperature shift, no LH surges, no fertile mucus), it's time to see a doctor. Treatments to induce ovulation are very effective:

Letrozole (Femara): First-line treatment for PCOS-related anovulation. Helps most women ovulate within a few cycles.

Clomiphene (Clomid): Another oral medication that induces ovulation. Works well for many women.

Metformin: Especially helpful for PCOS with insulin resistance. Can restore ovulation in some women, often combined with letrozole or Clomid.

Gonadotropins: Injectable hormones that directly stimulate the ovaries. Used when oral medications don't work.

⚠️ Don't Wait Too Long: If you've been trying for 12 months with irregular cycles (or 6 months if over 35), see a reproductive endocrinologist. If your periods are very infrequent (fewer than 6-8 per year) or absent, there's no reason to wait—treatment is needed to give you chances to conceive.

Lifestyle Changes That Can Help

For some causes of irregular periods, lifestyle modifications can restore regular ovulation:

Weight management: For PCOS, even 5-10% weight loss can restore ovulation in overweight women
Stress reduction: If stress is the cause, addressing it may bring back your cycle
Adequate nutrition: For hypothalamic amenorrhea, gaining weight and reducing exercise intensity may be necessary
Sleep hygiene: Regular sleep supports hormonal balance
Supplements: Inositol may help restore ovulation in PCOS; vitamin D supports overall hormonal health

💊

For PCOS & Irregular Cycles

Theralogix Ovasitol

Myo-inositol and D-chiro-inositol in the research-backed 40:1 ratio. Studies show inositol can help restore regular ovulation in PCOS. Often as effective as metformin for ovulation.

Check Price →

Where Are You in Your Journey?

Our quiz can help you understand your situation and point you toward the right resources.

Take the Fertility Quiz →

The Bottom Line

Irregular periods make timing conception harder, but they don't mean you can't get pregnant:

Find out why your cycles are irregular—basic blood work can identify treatable causes
Track your body's signals (cervical mucus, BBT) rather than relying on calendar predictions
Have sex when you see fertile signs regardless of what day it is
Don't wait too long to seek help—if you're not ovulating, you need treatment
Most causes are treatable—ovulation induction works very well

The main difference for women with irregular cycles is that timing requires more attention and help may be needed sooner. But the vast majority of women with irregular periods who want to become mothers are able to do so.

Frequently Asked Questions

Can I use ovulation predictor kits with irregular cycles?

Yes, but you may need to test for many days, which gets expensive. Start testing earlier than you might expect ovulation and continue until you get a positive (or your period comes). Note that with PCOS, you may get false positives due to chronically elevated LH. Combine OPKs with other tracking methods for better accuracy.

Will my irregular periods affect pregnancy once I conceive?

Usually no. Once you're pregnant, the underlying cycle irregularity doesn't typically affect the pregnancy. The main challenges with PCOS or other conditions relate to conceiving, not carrying a pregnancy. That said, conditions like PCOS may increase gestational diabetes risk, so monitoring during pregnancy is important.

Should I try to regulate my periods with birth control before TTC?

No—birth control masks the underlying problem without fixing it. It also prevents pregnancy while you're taking it. If you have irregular cycles, the goal is to understand and treat the cause, not artificially regulate with hormones that prevent ovulation.

How long should I try before seeing a doctor?

Standard advice is 12 months (6 if over 35), but with irregular cycles, consider being seen sooner—especially if you're having fewer than 8-9 periods per year or going months without a period. There's no benefit to waiting if you're not ovulating regularly.

My cycles used to be regular but became irregular. Why?

New-onset irregular cycles warrant investigation. Common causes include thyroid changes, significant stress, weight changes, the beginning of perimenopause (if in your late 30s-40s), or developing conditions like PCOS. A change in cycle pattern is a good reason to see your doctor and get some basic testing.