What is pregnancy and irregular periods?

You can tell if you're pregnant even if you have irregular periods with signs of pregnancy other than a missed period, such as implantation bleeding, nausea, swollen or tender breasts, fatigue, frequent urination, mood swings, headaches, backaches, and changes in cravings or aversions.
You can tell if you're pregnant even if you have irregular periods with signs of pregnancy other than a missed period, such as implantation bleeding, nausea, swollen or tender breasts, fatigue, frequent urination, mood swings, headaches, backaches, and changes in cravings or aversions.

Irregular periods can make it difficult to know whether you’re pregnant. It can make it harder to predict ovulation (when a mature egg is released from the ovary) or determine the best date to take a pregnancy test. Depending on the cause, women with irregular periods may also have greater difficulty getting pregnant.

Most women have menstrual cycles that are about 28 days long, give or take a few days on either end. Their cycles may change from month to month but will usually stay within that range.

An irregular menstrual cycle may be less than 24 days or greater than 38 days. Bleeding that lasts longer than eight days is also abnormal.

If you are concerned about irregular periods and pregnancy, there are signs of pregnancy other than a missed period and additional ways to determine when you are most likely to get accurate results with a pregnancy test.

Signs of pregnancy with irregular periods

If you are pregnant, you may experience any or all of the following symptoms of early pregnancy:

Implantation bleeding

Some women bleed at the time of implantation, which occurs about one or two weeks after fertilization. It can be easy to mistake the signs of implantation, which include cramps and bleeding, for a light period. Some things that can help you tell the difference are:

  • Unlike some periods, implantation bleeding never includes clots of coagulated, or semisolid, blood and tissue.
  • Implantation bleeding is very light in flow.
  • While period blood is reddish, implantation bleeding is pink or brown.
  • Implantation bleeding should only last one to three days.


Due to hormonal changes, nausea is one of the most common symptoms of early pregnancy, often starting as early as two weeks after conception. It may or may not be accompanied by vomiting. Low blood sugar levels in the morning often react with the hormones, leading to more frequent nausea in the morning.

Swollen or tender breasts

Some women first notice the effects of pregnancy hormones on their breasts, which can become swollen or tender.


During early pregnancy, your body is changing to accommodate the fetus, which can make you feel tired. Rising levels of progesterone (a hormone that regulates the menstrual cycle) can also contribute to fatigue.

Other symptoms

The following symptoms are less common in the first few weeks of pregnancy but may still occur during the first trimester:

Causes of pregnancy with irregular periods

Many women have irregular periods at some point between adolescence and menopause (when a woman’s period stops). Periods are often irregular during adolescence and during perimenopause (when your body makes the natural transition to menopause).

Other causes of irregular periods include:

When to see the doctor for pregnancy with irregular periods

You might see the doctor for irregular periods in any of the following cases:

  • Your period suddenly becomes irregular after being regular
  • You haven’t had a period for 90 days or more
  • You have a period more often than every 21 days or less often than every 35 days
  • Your period lasts for more than seven days
  • Your period is unusually heavy
  • Your period is incredibly painful
  • You bleed in between your periods

Your doctor will help determine the cause of your irregular period and suggest a course of action.


The first sign of pregnancy is most often: See Answer

Diagnosis for pregnancy with irregular periods

There are many causes of irregular periods, including pregnancy. While home pregnancy tests claim to be most accurate after a missed period, it can be difficult to know when you have missed a period if you’re irregular.

If you think you may be pregnant, try waiting either 28 days since you last had sex or 36 days from your last period. Take the test again a few days later if it is negative but you still think you may be pregnant.

In order to diagnose your irregular periods, your doctor may perform any of the following examinations or tests:

Your doctor will also take a detailed family and personal history to help them evaluate the results.

Treatments for pregnancy with irregular periods

The treatments for irregular periods vary based on the diagnosis and may involve treatment for an underlying disorder. The following types of irregular periods require different treatments:

The treatment for absent, infrequent, or irregular periods may include:

The treatment for heavy or prolonged periods may include:

The treatment for painful periods may include:

  • Nonsteroidal anti-inflammatory medications
  • Contraceptives
  • The application of a heating pad

Talk to your doctor about what treatment for irregular periods might be right for you.

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Medically Reviewed on 1/25/2021
American Pregnancy Association: "Early Signs of Pregnancy."

American Pregnancy Association: "What is Implantation Bleeding?"

Harvard Health Publishing: "Miscarriage."

Harvard Health Publishing: "When You Visit Your Doctor - Irregular Menstrual Periods."

Hormone Health Network: "Progesterone and Progestins."

Journal of Women's Health: "Perimenopause: From Research to Practice."

National Institutes of Health: "What are the common treatments for menstrual irregularities?"

Office on Women's Health: "Knowing if you are pregnant."

Office on Women's Health: "Pregnancy tests."

Penn Medicine: "Irregular Periods: Why Is My Period Late?"

Reproductive Endocrinology: "The normal variabilities of the menstrual cycle."

The American College of Obstetricians and Gynecologists: "Abnormal Uterine Bleeding."