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Getting Pregnant

How to Get Pregnant Fast With Irregular Periods

getting pregnant with irregular periods

With an irregular period, you may wonder how fast you can get pregnant. This may be especially true if you’re not exactly sure when you ovulate from one cycle to the next.

Although getting pregnant with irregular cycles may take longer, it’s doable. Here’s what you need to know to figure out why your periods are irregular, manage your cycles naturally, time sex — and get pregnant in no time.

What is a “normal” menstrual cycle?

Menstrual cycles range from about 25 – 36 days. The idea of a 28-day cycle is totally outdated — only 10-15% of women have cycles that are precisely that length. Menstrual cycles may vary a few days each month and still be normal. 

Lifestyle changes, including stress and travel, can cause an occasional irregular cycle. But in some women, irregular periods are the norm.

What is an irregular cycle? 

An irregular cycle is one that’s either shorter than 24 days, longer than 38 days, or one that varies more than 7-9 days from one cycle to the next

Irregular cycles are common. At least one in five women have irregular menstrual cycles that are longer or shorter than the norm.

woman in bed

To see if you have irregular periods, count the days in your cycle. Start counting on day one, which is the first day of menstrual bleeding, and stop counting the day before your next period starts. The number of days you counted is your cycle length. Bear in mind, length may vary from one cycle to the next.

What causes irregular cycles?

There are myriad reasons for irregular periods, but the most common reasons include:

  • Anovulation: Anovulation is where the ovaries don’t release an egg during menstruation. It can be caused by several factors, including extreme stress, exercising too much, or being underweight or overweight.
  • Polycystic ovarian syndrome (PCOS): PCOS, a hormonal imbalance, causes heavy or irregular cycles, and is the leading cause of female infertility.
  • Thyroid imbalance: The thyroid, a hormone-releasing gland in your neck, can cause irregular periods and infertility when it’s overactive or underactive.
  • Too much prolactin: Abnormally high levels of the hormone prolactin are necessary for breastfeeding, but in women who aren’t breastfeeding, too much prolactin can change or stop ovulation, producing irregular or absent periods.
  • Short luteal phase: The typical luteal phase (after ovulation) is 14 days, and one shorter than this can produce irregular cycles. With a luteal phase that’s consistently shorter than 10 days, it may take longer to get pregnant.
  • Premature ovarian failure (POF): POF occurs when the ovaries slow down or stop releasing eggs before age 40. 
  • High BMI: Obesity can lead to anovulation and is linked to period-disrupting conditions, like PCOS. 
  • Low BMI: Being significantly underweight can lead to irregular periods and fertility challenges. 
  • Exercise: Up to half of exercising women may experience menstrual disturbances, such as irregular cycles and anovulation. Separate research doesn’t necessarily suggest exercise is bad, but rather that inadequate fueling for activity level can be problematic.
  • Stress: Physical stress may cause irregular cycles, while psychological stress may cause delays in becoming pregnant.
  • Stopping the pill: Coming off hormonal birth control pills may lead to a short window of long menstrual cycles or irregular cycles.
  • Early menopause: The average age of menopause is 51, but early menopause occurs when a woman stops ovulating before then. One sign of this is irregular periods.

Can you get pregnant if you have an irregular period?

It’s possible to get pregnant with irregular periods, but it may take more time. One study found that women with highly variable (a.k.a. irregular) cycles were 51% less likely to get pregnant per cycle than women with regular cycles. 

A separate study, however, found irregular cycles made less of a difference in trying to conceive. In it, most women who got pregnant had cycles lasting 31 days, and women whose cycles were shorter or longer than 31 days also became pregnant, just at a slightly lower rate.

Irregular periods don’t necessarily mean you won’t be able to get pregnant on your own. Sometimes, making lifestyle changes can regulate previously erratic periods and help you conceive. Some women with irregular periods, however, will need to use fertility treatments. 

How do you track ovulation with irregular periods?

There are three main methods to track ovulation to give you a greater understanding of your cycle and to help you time sex to get pregnant faster.

Ovulation tests

Ovulation tests analyze urine for the presence of luteinizing hormone (LH). A surge of this hormone suggests ovulation may happen in the next 24 hours. 

However, ovulation tests are harder to use with irregular cycles because it’s not clear when ovulation may happen. As a workaround, start testing a few days after your period ends.

Beyond that, try not to rely solely on ovulation tests to time sex if you want to get pregnant fast. If you wait to see the LH surge to have sex, you may have already missed the ideal window to become pregnant. 

Cervical mucus

Consider also tracking your cervical mucus, which is vaginal discharge that follows a pattern during your menstrual cycle. Cervical mucus becomes more wet, slippery, and stretchy closer to ovulation. 

Tracking cervical mucus has been shown to be a highly accurate method for timing sex. But with irregular cycles, you may observe several patches of fertile mucus before successfully ovulating. 

That’s why you’ll also want to track your basal body temperature. 

Basal body temperature

Basal body temperature (BBT) is the body’s resting temperature. To chart your BBT, take it first thing in the morning — before you do anything — and do this at the same time every morning throughout your cycle. 

A slight increase, usually half a degree to a whole degree Fahrenheit, means ovulation has happened. Because the temperature increase happens after ovulation, BBT can’t help you time sex with irregular periods, but it can help you understand your body’s overall timing for ovulation in future cycles.

When to have sex to get pregnant with irregular periods

Timing sex can help you get pregnant naturally with irregular periods. For the best odds at conception, make sure to have sex on the days with fertile cervical mucus. It’s common to experience different types of mucus during the day, so check as often as your schedule allows.

When should I take a pregnancy test with irregular periods?

Irregular periods can make it hard to judge when to take a pregnancy test. According to the FDA, as many as 20 women in 100 will not detect a pregnancy on the first day of their missed period, partly due to irregular cycles.

One option is to test 36 days after the start of your last menstrual cycle or 28 days after having sex. By then, the level of the pregnancy hormone human chorionic gonadotropin (hCG) should be high enough to detect a pregnancy.

If you don’t want to wait that long, one OB/GYN suggests taking a pregnancy test 14 days after having sex. If it’s negative, repeat it in about a week. 

How can I regulate my period naturally?

Treatment varies, depending on the reason behind the irregular cycles. If the cause is a lifestyle factor, you can try:

  • Easing up on exercise
  • Reducing stress
  • Gaining weight
  • Losing weight

One small study of women with PCOS and obesity found that most of the women began ovulating regularly and went on to become pregnant after losing around 13 pounds. 

For some women, however, fertility treatment is necessary to get pregnant with irregular cycles. 


View sources

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American College of Obstetricians and Gynecologists. Fertility Awareness-Based Methods of Family Planning. 2019.

Merck Manual. Menstrual Cycle. 2019.

Small, C.M., Manatunga, A.K., Klein, M., Dominguez, C.E., Feigelson, H.S., McChesney, R., & Marcus, M. Menstrual cycle variability and the likelihood of achieving pregnancy, Reviews on Environmental Health, 2011.

Lum, K. J., Sundaram, R., Buck Louis, G. M., & Louis, T.A. A Bayesian joint model of menstrual cycle length and fecundity, Biometrics, 2016.

De Souza, M.J., Toombs, R.J., Scheid, J.L., O'Donnell, E., West, S.L., & Williams, N.I. High prevalence of subtle and severe menstrual disturbances in exercising women: confirmation using daily hormone measures, Human Reproduction, 2010.

Loucks, A.B., Verdun, M., & Heath, E.M. Low energy availability, not stress of exercise, alters LH pulsatility in exercising women, Journal of Applied Physiology, 1998.

Bigelow, J.L., Dunson, D.B., Stanford, J.B., Ecochard, R., Gnoth, C., & Colombo, B. Mucus observations in the fertile window: a better predictor of conception than timing of intercourse, Human Reproduction, 2004.

Jungheim, E.S., Travies, J.L., Carson, K.R., & Moley, K.H. Obesity and reproductive function, Obstetrics and Gynecology Clinics of North America, 2012.

U.S. Food and Drug Administration. Home-use pregnancy tests. 2019.

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Clark, A.M., Ledger, W., Galletly, C., Tomlinson, L., Blaney, F., Wang, X., & Norman, R.J. Weight loss results in significant improvement in pregnancy and ovulation rates in anovulatory obese women, Human Reproduction, 1995.

Nicole Knight

Nicole Knight is a California-based freelance healthcare writer and award-winning journalist. Her bylines have appeared in the Guardian, Los Angeles Times, and Rewire.News, among others. She is a member of the Association of Health Care Journalists and the American Society of Journalists and Authors. Find her on Twitter @nicolekshine.

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