The Menstrual Cycle

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Getting to know your menstrual cycle, allows you to understand the pattern of events that take place in your body, each cycle.

Knowing how long your cycles are, when you're fertile and when you ovulate will help you achieve your goal of getting pregnant or avoiding pregnancy.

What is the menstrual cycle?

The menstrual cycle is a cycle of changes that your body goes through as it prepares to conceive each cycle.

This includes building a uterine lining for a fertilized egg to implant and begin growing; releasing an egg to be fertilized, and shedding the uterine lining if the egg is not fertilized. These changes collectively are called the menstrual cycle and are controlled by hormones.

All about cycle lengths

The terms menstruation and menstrual are derived from the Latin word for month, which in turn relates to the Greek word mene, meaning moon. There is much written historically describing menstruation and how it is believed to coincide with the new moon.

The average menstrual cycle length is 28 days, but they can vary in length from 23 days or less in a short cycle, to over 35 days in a long cycle.

Day one of your cycle is the first day of your period and this continues right up to the day before your next period.

Here is something you may not know... Most women ovulate 15 days BEFORE their next period. How is this so?

The menstrual cycle is divided into phases (more detail on this later), the phase before ovulation, the follicular phase, varies in length from women to women and can even vary for the same women, varying from about 13 to 20 days long.

However, the phase after ovulation, the luteal phase, is the same for most women (12 to 16 days long with the average being 14), and stays consistent for the same women.

Cycle Length showing Varying Follicular Phase, Consistent Luteal Phase

Quick overview of how hormones control your cycle

Your menstrual cycle is under the control of two very important structures in your brain: the 'hypothalamus' and the 'pituitary gland'. Here is a quick overview of what happens...

  1. Your 'hypothalamus' produces Gonadotropin Releasing Hormone (GnRH) at the beginning of each cycle.
  2. GnRH acts on your 'pituitary gland' to produce Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH).
  3. LH & FSH then travel to your ovary to induce ovulation. After ovulation they cause the empty follicle to release Estrogen and Progesterone.
  4. Estrogen and Progesterone make your uterus lining moist and thick, in preparation for implantation of a fertilized egg.

I'll be covering the details of what happens during the menstrual cycle, but if you would like to know more about hormones specifically, click here.

As well as controlling what happens during your menstrual cycle, your hormones can also impact your mood. Some women experience extreme mood changes throughout their cycle and some may not really notice any fluctuations.

Follicle Stimulating Hormone (FSH) which in turn stimulates the ovary to develop egg follicles. As these follicles grow and start to mature, they produce the hormone oestrogen. Just before the middle of the cycle oestrogen levels start to rise. This causes a sudden increase in Luteinising hormone (LH). The rise in LH triggers the rupture of the maturing follicle and releases the egg at ovulation. The egg only lives for a maximum of 24 hours and most likely only as short as 12 hours. The hormone progesterone then kicks into action. If conception does not occur, the levels of progesterone will fall just before the next menstrual period.

Phases of the menstrual cycle

The menstrual cycle can be described as a series of events that happen in the uterus AND ovary. These are known as the Uterine Cycle and Ovarian Cycle. Each of these cycles have three phases:

- Uterine Cycle Phases: MENSTRUAL > PROLIFERATIVE > SECRETORY
- Ovarian Cycle Phases: FOLLICULAR > OVULATION > LUTEAL

Uterine Cycle and Ovarian Cycle

See the table below to learn more about the phases. Being aware of these events can help you know when your are most fertile and help you get pregnant.

The following table shows the series of events in a typical 28 cycle. Note: If you have a shorter or longer cycle, the length of the phases before ovulation will be shorter/longer.

Cycle Days Uterine Cycle Phase Ovarian Cycle Phase
1-5 MENSTRUAL PHASE: Your uterus shreds the lining (endometrium) that was built in the previous cycle in preparation for a new lining. FOLLICULAR PHASE: A few follicles (nurturing capsule containing undeveloped egg) are stimulated by LH and FSH to grow in the ovary. One will become the dominant follicle that will release an egg during this cycle. The others will stop growing. See follicle development.
6-12 PROLIFERATIVE PHASE: Estrogen and Progesterone make your uterus grow a new lining. FOLLICULAR PHASE: Estrogen causes the dominant follicle to continue to grow, it quickly grows in size. Estrogen also causes your cervix to change and produce cervical mucus.
13-14 PROLIFERATIVE PHASE: Your new uterus lining (endometrium) continues to grow. OVULATION PHASE: Rising levels of Estrogen trigger a surge of LH which provides the egg in the follicle with a final push to mature before it's released (ovulation).
15-20 SECRETORY PHASE: Progesterone causes the endometrium to thicken in preparation for possible implantation of a fertilized egg. LUTEAL PHASE: After ovulation the egg moves down the Fallopian tube towards the uterus. The empty follicle (now called the corpus luteum) stays in the ovary and produces Progesterone. Progesterone is also responsible for your Basal Body Temperature to rise.
21-28: If the egg was not fertilized SECRETORY PHASE: Progesterone levels drop; the endometrium starts to break apart until it can no longer support itself. The endometrium is then shed again (beginning of a new cycle). LUTEAL PHASE: The corpus luteum stops producing Progesterone.
21-28: If the egg was fertilized SECRETORY PHASE: About 8 days after ovulation the fertilzed egg attaches itself to the wall of the uterus (this is called implantation). LUTEAL PHASE: The corpus luteum receives 'human Chorionic Gonadotropin' hormone (hCG) from the embryo. hCG makes the corpus luteum keep producing Progesterone for about 8 more weeks, after which time the placenta takes over Progesterone production throughout pregnancy.

More about the luteal phase


After ovulation, the remains of the dominant follicle (that released the egg), transforms into the corpus luteum. The corpus luteum starts to produce significant amounts of hormones, particularly Progesterone. The hormones maintain the thickened lining of the uterus, waiting for a fertilized egg to implant. If implantation does not occur, the corpus luteum withers and dies which causes Progesterone levels to drop, this then causes the uterus lining to break up resulting in menstruation, and so a new cycle begins.

Calculating your luteal phase length

Your luteal phase begins on the day after you ovulate, and runs through the rest of your menstrual cycle, ending the day before your next period. As mentioned, the luteal phase usually lasts 12-16 days. Your follicular phase can often vary in length from cycle to cycle; by contrast, your luteal phase will be fairly consistent.

If you have visited our online community forum, you may have encountered the acronym, "DPO". This is another way of referring to the luteal phase, it means Days Past Ovulation. When the luteal phase begins, your basal body temperature (BBT) increases in order to provide a more fertile environment for a fertilized egg.

If you do not know whether you have an average or short luteal phase, start by assuming the 14 day average. Follow these steps to detect ovulation. Once you know when you have ovulated, you can start tracking your luteal phase. The number of days from the day after ovulation to the day before your next period is the number of days in your luteal phase.

What to do if you have a short luteal phase

For most women, the luteal phase usually last 14 days, but anywhere from 10 to 16 days is considered normal. If yours happens to be shorter than 10 days, it may be too short for successful implantation to occur. A luteal phase defect or luteal insufficiency occurs when the luteal phase is shorter than normal or when the lining of the uterus is not prepared for implantation. Women who are trying to conceive that have a short luteal phase are often treated with progesterone therapy, and some women have found success with other natural remedies. See below for further information.

When does implantation occur?

Implantation will only occur if an egg becomes fertilized, if a sperm does not penetrate the egg within 12 to 24 hours of ovulation, implantation will not occur during the cycle.

If the egg does become fertilized, it starts dividing and making the slow journey from the fallopian tube to the uterus (about three to four days). Once the fertilized egg reaches the uterus it makes it way to the side wall and implantation begins. This is where the fertilized egg begins burrowing into the plush uterine wall (about 8 days after fertilization). Some women notice slight bleeding or spotting at this time called implantation bleeding.

Luteal phase defect

A luteal phase defect occurs when the luteal phase is shorter than normal or when the lining of the uterus is not prepared for implantation. This may happen if the ovary is secreting lower levels of progesterone than normal or if the lining of the uterus simply is not responding to the normal stimulation of progesterone from the ovary. Given that implantation is a crucial part of early pregnancy, a luteal phase defect can severely impact pregnancy.

Luteal phase defect symptoms

Symptoms of luteal phase defect include: shorter cycles and having periods more frequent, trouble getting pregnant and bleeding.

If your doctor suspects a luteal phase defect, they may assess the endometrial cells of the uterine lining around two days before you are due to menstruate. From here, your doctor can evaluate the quality of your endometrium. Your doctor will also ask you to notify them when you get your period. If the biopsy is taken on day 26 of a 28-day cycle and you get your period two days later, your luteal phase is considered "in phase", or normal. If you get your period on day 27 or after day 29, you will be considered "out of phase" and a luteal phase defect will be diagnosed. Since it is common for women to have a cycle that is off by a day or two, at least two biopsies are usually taken during two or more cycles before a diagnosis can be made.

Luteal phase defect treatment

Your doctor may use clomiphene citrate or human menopausal gonadotropins (hMG) to stimulate follicular growth; supplement with hCG to improve progesterone secretion; or provide you with progesterone supplements, by injection, orally or vaginally after ovulation.

Normal menstrual cycle symptoms

Over the course of a normal menstrual cycle, there are many physical changes that you may notice in your body. These can vary woman to woman and even cycle to cycle, but may include:

What factors may affect normal menstrual cycle symptoms?

There are many things that might alter your symptoms and how you experience your cycle. This can include the form of birth control that you may be using, other medications, and your general health. If you have any serious changes in your cycles, you should report it to your doctor as it may indicate that you have a problem.

Are you in tune with your menstrual cycle? Want to ask a question or leave a comment? Please do so below.

New Join the Discussion!

  1. Marie Jul 28, 2016
    I just see my period today again because i'm irregular, the last period start July 8/16 and end July 12/16. Today is July 28/16.
    1. Sarah (OC Team): Thanks for commenting Marie. - (Jul 28, 2016)
    2. Eam: I need help. Last August, I had my period on the 21st. Then in Sept, I had it on the 25th and my cycle usually is 35 days at the longest. Basically, a 30 day cycle normal. I had this bothering me. It said I will have my period on the 25th of October, but its almost the end of Oct now and I still dont have a period. But last Oct 21, I saw brown spotting and milky discharge. It looked like my menstruation coming, but unfortunately, it lasted for a half day and no more. It only left a small dot on my napkin. I'm so confused - (Oct 30, 2016)
    3. Christina (OC Team): Have you taken a pregnancy test? - (Oct 30, 2016)
    4. Eam: No I didn't... how about the cervix position? Is it low or high? Thanks - (Oct 31, 2016)
    Reply
  2. Ogom Aug 09, 2016
    I am confused! Another cycle started today. The last cycle started on 14th of July. These days, menstrual symptoms are so like pregnancy symptoms. Would I know the difference when I am indeed pregnant?
    1. Christina (OC Team): It's true that menstrual symptoms are often similar to very early pregnancy symptoms. The only way to know for sure is to wait and test. You may also find this article about implantation vs. period helpful. https://www.ovulationcalculator.com/implantation-bleeding-or-period-quiz/ - (Aug 09, 2016)
    Reply
  3. Mary Aug 17, 2016
    I really like this forum. And I learned a lot here. I have experienced implantation bleeding, but I did not really understand what It is. Now am in a 28 day cycle. There's a pain I always experience a day after my ovulation. It's on my left side. Please, I want to ask if this pain is normal or if it can affect pregnancy. Thank you.
    1. Christina (OC Team): Is it possible that you're feeling cramping on the day of ovulation (the day after EWCM)? This could be a symptom of ovulation. Have a look at this article: https://www.ovulationcalculator.com/ovulation-symptoms-signs/ - (Aug 17, 2016)
    Reply
  4. Nikky Aug 20, 2016
    Another cycle started today and am sad. I thought I have conceived. Every month, I always have signs that I am pregnant. Sometimes, there will be a delay in my cycle. Please, is this normal?
    1. Christina (OC Team): When we're hoping and looking for signs, it's perfectly normal to notice things we've never noticed before. And cycles can vary. I'd suggest tracking your cycle here and with an OPK or BBT. Especially if your cycles vary in length, you want to be sure to pinpoint your precise fertile window. Here is an article on charting BBT https://www.ovulationcalculator.com/basal-body-temperature/ And here is an article that I hope may help lift your spirits https://www.ovulationcalculator.com/infertility-inspiration/ Good luck! - (Aug 20, 2016)
    2. Nikky: Thanks and God bless. - (Sep 04, 2016)
    Reply
  5. Mary Aug 21, 2016
    Another cycle started today. For two months, my cycle was 28 days. Last month, it was 27 days. But my period is dark red. And it's light not heavy and lasted for 3 days. Advise me.
    1. Christina (OC Team): Take the implantation vs. period quiz here: https://www.ovulationcalculator.com/implantation-bleeding-or-period-quiz/ - (Aug 22, 2016)
    Reply
  6. Tashia Aug 29, 2016
    Quick question, I got another period 15 days after my former period...and it lasted 5days, but the bleeding was not as heavy as it usually (I was on some weight drugs). Should I start counting from this new date or wait till my regular date again?
    1. Christina (OC Team): I'd suggest logging from your most recent period. - (Aug 29, 2016)
    Reply
  7. Marjs Aug 30, 2016
    I always experience pain a day before.
    Reply
  8. Claudia Sep 02, 2016
    If someone had intercourse today and got her period tomorrow, can she still be pregnant?
    1. Christina (OC Team): She must have had sex during her fertile window, which usually occurs around 15 days before the next period, in order to conceive. - (Sep 02, 2016)
    2. Claudia: Means she can't be pregnant. - (Sep 10, 2016)
    Reply
  9. Mabel Sep 05, 2016
    If I was on a contraceptive, how long will it take before I conceive?
    1. Christina (OC Team): It depends on many things, including the method. Have a look at this article for more information: https://www.ovulationcalculator.com/getting-pregnant-after-birth-control/ - (Sep 06, 2016)
    Reply
  10. Damilola Sep 07, 2016
    I have six days to my next period, but I am having slight pain in my lower abdomen. Could it be that I am pregnant? Please, I want an answer because I had sex during my fertile window.
    1. Christina (OC Team): If you had sex within your fertile window, pregnancy is a possibility. However, only a test can tell you for sure. Good luck! - (Sep 07, 2016)
    Reply
  11. Eddy Sep 17, 2016
    I had my period today, Sep,17. The last was Aug,18. I've not seen my period for over 3years. I'm on cabergoline, which helps with my high prolactin. How can I improve my chances to conceive. Thanks, could I have egg health issues?
    1. Christina (OC Team): If you are taking a medication that impacts your cycle, you should talk to your doctor about how this impacts your chances of conceiving. Good luck! - (Sep 17, 2016)
    Reply
  12. Abbey Sep 27, 2016
    Thanks for this knowledge.
    1. Christina (OC Team): Glad we could be of help. :) - (Sep 27, 2016)
    Reply
  13. Leah Sep 27, 2016
    If I have sex the day after my period ends, can I get pregnant?
    1. Christina (OC Team): This would depend on the length of your cycle and when you ovulate. If you have a short cycle and a long period, it's likely that the day after would fall within your fertile window. - (Sep 27, 2016)
    Reply
  14. Juli Oct 04, 2016
    I had my period on the 6th of September. When will i be excepting it this month? My cycle is 28 days. Thanks and God bless you.
    1. Christina (OC Team): 28 days after the six is the 3rd. If you want to track your periods and ovulation, enter your cycle dates into your account here. - (Oct 04, 2016)
    Reply
  15. Ijeoma Oct 05, 2016
    My last period was on the 11th of Sept and now it started today. That is 25 days today. It normally lasts for 3 days and the 4th day is just a little. I want to know if it is normal and when will I be in my fertile window? How will I know?
    1. Christina (OC Team): I'm not sure I understand. Have you bled for 25 days? If so, you should talk to your doctor. - (Oct 05, 2016)
    Reply
  16. Sheena Oct 05, 2016
    Never thought it would be this hard to get pregnant. When I got pregnant with my daughter, it came so easy. Why? Because it was not planned. Now, it's 7 years later. This is something that is planned and can't seem to happen. My fiance and I have been trying for 4 months straight now and nothing. My cycle has always be pretty spot on 28-29 days. Now, for the last 3 months, I have been at a 26 day cycle. This month, I started back at 28 days. I'm hoping my cycle is back to normal, so we know what ovulation days we can go off of. Also, I was told since I'm a 34-year-old woman, I can start having false ovulation?? I've never missed my period, so I'd assume if I'm having my period then I'm still ovulating??
    1. Christina (OC Team): If you are getting your period, there's a good chance you are ovulating. I'd suggest trying OPKs (over-the-counter Ovulation Prediction Kits). These will tell you if, and approximately when, you are ovulating. - (Oct 05, 2016)
    Reply
  17. MARY Oct 06, 2016
    I had sex on day 20 and the length of my cycle is 27 days. Can I get pregnant? Thanks.
    1. Christina (OC Team): If you're trying to conceive, log your cycle dates into the calculator here and get a prediction of your fertile window. In order to conceive, or know if you have a chance, you must know when you ovulate. - (Oct 06, 2016)
    Reply
  18. Preethi Oct 21, 2016
    Hi,
    I am having light brown discharge 4 days before my period and slowly it turns into normal menstrual flow. I have regular 30 days cycles and bleeding is normal. But I am worried about this discharge and spotting 4-5 days before my periods. Does this indicate low progesterone? I am ttc for just a month but still concerned and worried.
    1. Christina (OC Team): Spotting could be an indication that implantation has occurred. Have a look at this article https://www.ovulationcalculator.com/implantation-bleeding-or-period-quiz/ - (Oct 21, 2016)
    2. Preethi: I got a BFN. I have been observing this for the past 6-8 months. Could it be due to hormonal imbalance or luteal phase defect? - (Oct 21, 2016)
    3. Christina (OC Team): I'd suggest asking your doctor, especially if this is a regular occurrence. - (Oct 22, 2016)
    Reply
  19. Tope Oct 25, 2016
    Hello, please I need your help. I have been having irregular periods for some months now. My last period for Sept was on the 23rd and this month came today (25th). I now find it difficult to calculate my ovulation. I am so confused and eager to get pregnant. While my period was late this time I had different symptoms thinking I was pregnant. What should I do?
    1. Christina (OC Team): Irregular periods can make tracking difficult. I'd suggest using OPKs to find out when you are about to ovulate and keep tracking. Your luteal phase, the days between ovulation and menstruation, should remain the same every cycle. So once you learn approximately when you ovulate, you can estimate when your next period will come. Have a look at this article to learn more about your luteal phase https://www.ovulationcalculator.com/ovulation/ - (Oct 26, 2016)
    Reply
  20. Tope Oct 30, 2016
    Thanks
    Reply
  21. Oladunni Nov 01, 2016
    I have been vomiting since day 21 of my menstrual cycle. My nipples hurt too.
    1. Christina (OC Team): I'm sorry to hear you've been sick. You may want to talk to your doctor. Feel better soon! - (Nov 01, 2016)
    Reply
  22. Janice Nov 01, 2016
    Hello, I had sex in my fertile days. 10 days later, I had light pink spotting and have had headaches now on 11/01/16. My period started and I have had my period and was still pregnant. Could I possibly be pregnant?

    1. Christina (OC Team): If you think you may be pregnant, try testing. Good luck! - (Nov 02, 2016)
    Reply
  23. Peace Nov 05, 2016
    My last period was on the 23rd of October. I have a 28-day cycle and I had sex on the 11th, 13th, and 14th. What is my chance of getting pregnant?
    Reply
  24. Kim Nov 06, 2016
    I'm not do for my period for 8 days. I just started bleeding. Not spotting, but bleeding. I'm very worried. I've been trying to conceive for about 4 months now.
    Reply
  25. Peace Nov 06, 2016
    My last test date was on October 23rd, and I had sex on the 11th, 13th, and 14th day. What are my chances of getting pregnant?
    1. Christina (OC Team): If you create an account with Ovulation Calculator, you can get an estimate of your fertile window. - (Nov 07, 2016)
    Reply
  26. Heidi Nov 09, 2016
    Help, both of my apps say my period was due the 7th of October and it is now the 9 and I haven't seen it. BUT I had sex was the whole week before my last period, so I don't think I'm pregnant. But I'm confused.
    1. Christina (OC Team): It's possible that your period is late, but you can take a test to see if you are pregnant. - (Nov 09, 2016)
    2. Hawee: Hi, my period was 4 days late, but on the 5th day, it started. This made my last cycle 33 days long instead of the regular 29 days. I am worried. Why is this so? What are the consequence of these changes on my chances of conceiving /fertility? Thanks - (Nov 11, 2016)
    3. Heidi: Still haven't gotten my period and it's been 9 days. I took a PT and got a negative a few days ago. Should I re-test ? - (Nov 16, 2016)
    Reply
  27. Peace Nov 10, 2016
    The 23rd of Oct was my last period. It was a 28 day cycle and my fertile days were from the 1st - 6th November. I had sex on the 2nd, which was on the 11th, 13th and 14th. Do I have any chance of getting pregnant?
    Reply
  28. Madi Nov 26, 2016
    During your menstrual phase, should you chart "none" for your CF and "no" for spotting?
    1. Christina (OC Team): Yes, you can chart none for CF and no for spotting. - (Nov 28, 2016)
    Reply

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