What Could Cause an Abnormal Period?

An Abnormal Period Doesn't Always Mean You're Pregnant

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Short Period and Other Reasons to Take a Pregnancy Test. Photo © The Image Bank/Getty

You know your period. You know when to expect it, how to calculate the number of pads or tampons you will need, and you probably even know what you can get away with wearing in terms of clothes, based on your flow. It's likely that you would know if your period were abnormal in any way.

While an abnormal period may be normal once in a while, it's undoubtedly stressful. Understanding what is going on in your body that's causing the irregularity can help.

What Is an Abnormal Period?

A period that is abnormal is one that is in some way different from a typical, normal period, but this could mean different things.

For example, your period could be longer or shorter or may come earlier or later than anticipated. It may be different in the amount of flow. You may also find that it stops and starts, even if overall it lasts the same number of days. Basically, anything that isn't what you would expect is abnormal and should be watched.

What Causes an Abnormal Period?

There are a number of things that cause your period to be different, including:

  • stress
  • increased or decreased exercise
  • change in sleep patterns
  • new medications
  • illness
  • pregnancy

For many women, pregnancy is top of mind as the reason for an abnormal period. Though it certainly is a possibility, it may not be the most likely scenario for you based on your use of birth control and sex life, and as you can see, simple changes in your day-to-day life could cause variances.

An example of this might be a woman who is taking oral contraceptives, the pill, and has an unusual period. She takes her birth control pills regularly and has not missed any days, nor had a medication change that would alter her birth control status. If her period is lighter or shorter, it is more likely simply a result of less build up in her endometrium (uterine lining), than pregnancy.

Certainly pregnancy could be an option, but it doesn't make it the most likely option.

Sometimes, our bodies behave oddly when we’re pregnant. This can make your period come but in a different than normal manner. It might be late or light. It might be heavy but short. It might only be spotting. A short period might mean you're pregnant. These can all be signs of a pregnancy. The only way to sort out the pregnancy from the rest of the reasons would be to take a pregnancy test. Sometimes what a woman mistakes for her period is really what we call implantation bleeding, a slight bleeding that occurs and the baby implants into your uterus.

What if you are pregnant and had a period?

How do women confuse their periods with pregnancy? One thing we have learned as women from a very small age is that pregnancy means you won't have a period. So any disruption in our period means pregnancy in our minds. This happens in a couple of ways.

Sometimes the bleeding you have isn't your period. This could be that you've thought of bleeding as a period, when it was really implantation bleeding. This is bleeding that occurs around the time the fertilized egg is burrowing into your endometrium. This may look like spotting and confuse someone into thinking they had a really light period, until they miss their second period.

You may also be having bleeding because you are pregnant and something is going on. This might be a hormonal issue, or impending miscarriage that requires you to get care from a doctor or midwife. 

What if your period is abnormal?

The best thing to do is to take a pregnancy test if you think your period was weird. If it's negative, wait for your next period. If it is also weird, consider seeing your doctor or midwife for an exam to help get to the bottom of the weirdness.

Your Period is Late

This one may seem obvious, but there are a large number of women out there who choose not to take a pregnancy test when they think their period is late.

Some may be trying to avoid the false positives from early miscarriages (chemical pregnancy), but others simply think that they are late for a reason other than pregnancy. There are reasons that your period is late and don’t involve pregnancy.

When to See Your Doctor or Midwife

You can also call on your doctor or midwife any time you have a question about your menstrual cycle. This is particularly true if you are trying to get pregnant and notice that your cycle length is shorter than twenty-five days. You may also want to seek advice if you have erratic cycle lengths. You should also see your practitioner if you have been trying to conceive for over a year with no luck, if you are under thirty-five. If you are over thirty-five, they recommend that you wait no more than six month.

You will want to seek emergency assistance if your cycle flow has you soaking a pad or tampon every half an hour.


Obstetrics: Normal and Problem Pregnancies. Gabbe, S, Niebyl, J, Simpson, JL. Sixth Edition.

Ovulation Calendar. March of Dimes. http://www.marchofdimes.org/pregnancy/ovulation-calendar.aspx Last Accessed May 18, 2017.

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