Menstrual Cycle

Natural ovulation cycles

Every month from puberty to menopause, an egg is released from a follicle within one of your ovaries. In natural ovulation, each month your ovary starts to grow several follicles, one of which becomes dominant.

Two hormones are responsible for the development of follicles within your ovaries:

  • Follicle stimulating hormone (FSH), and
  • Luteinising hormone (LH)

The cells in the follicles also produce oestrogen and progesterone. Your hormone levels will rise and fall at different stages of your monthly cycle. If the egg meets a sperm somewhere in your fallopian tube, fertilisation may occur. Once cell division begins, an embryo travels down the fallopian tube to your uterus, where it should implant in the endometrium. This typically happens about seven days after ovulation.

Your pregnancy window

When you get your period, the ovary starts to develop a number of follicles, one of which will become dominant. A follicle is a small fluid-filled sac containing an egg.

Ovulation occurs after about 14 days on average, when the egg matures and is released. The egg can survive for about 8 hours in the Fallopian tube, where it can be fertilised by a sperm.

Your pregnancy window is the fertile time leading up to ovulation and fertilisation.

Once you know your pregnancy window, ensure you have sexual intercourse at least every two days during that time. Sperm will survive and retain fertilising ability for two to three days in the Fallopian tubes.

We don’t recommend using temperature charting as your temperature rises after you ovulate, and you need to have intercourse before ovulation. If you are concerned about your menstrual cycle, we can carry out tests to see what is happening.

When do I know when I ovulate?

Every woman is different, and your cycle may also vary month to month. Typically, an ovulatory cycle will be between 24 and 35 days in length. The time from the start of your period to ovulation could be as short as eight days, or as long as 21 days. The time from ovulation to menstruation is more consistent at 11 to 17 days, with an average of 14 days.

To work out when you ovulate, subtract 14 days from the number of days in your cycle. So if your cycle is usually 28 days, you can expect to ovulate on day 14 (between day 12 to 16). It might be helpful to use a urine ovulation detection test during your pregnancy window.

What causes infertility?

Infertility has been historically defined as a couple not conceiving after 12 months of regular unprotected sexual intercourse. Current data show that most couples will conceive within six months of trying, so best practice now suggests you seek a fertility assessment if you are not pregnant within six months.

Apart from increasing female age, infertility can be caused by problems within the female reproductive system, such as ovulation failure, tubal disease or endometriosis (about 40% of cases), or with sperm (again, about 40% of cases). In at least a third of cases there are both male and female factors causing problems.

Female Reproductive System

Understanding the female reproductive system

Understanding your ovulation calendar


Understanding Your Ovulation Calendar - Fertile Minds Video

Dr Joseph Sgroi:

We spend so much time at school learning about English, maths, biology, but very few of us know about our natural cycle. So today's topic is all about understanding your natural cycle and when you're ovulating.

Now, a woman's cycle, generally speaking is somewhere between 28 to 35 days. If your cycles are either shorter or longer than this, please contact your general practitioner and make a referral to see a fertility specialist so that we can have a look and see what's happening with your cycles. Women should really consider several things when they're trying to become pregnant, and I utilise a little acronym called SSROOP.

The first one is sex, and timing sex around ovulation is particularly important. And we'll talk a little bit about ovulation towards the latter part of this presentation.

And of course, it does take two to tango. So we do need sperm. That's the other S, and of course, not only does the sperm need to be healthy, swimming in a forward progression, but also there needs to be a good amount of good looking sperm that has the ability to fertilize an egg.

The next thing is a receptive uterus; a uterus that's structurally normal with no impediment for pregnancy. So when you see any one of us as fertility specialists, we're going to be asking questions about your menstrual cycle. If they're heavy, alternatively, if you have any pain, and this may give us an indication as to whether you might have things like endometriosis.

Of course, you need to have open tubes because the tubes are particularly important because they're the conduit or the pathway where the sperm and the egg can make. And fertilisation of the egg actually occurs in the tube itself.

And lastly, you need to ovulate. So let's talk a little bit about ovulation. A woman's cycle commences on day one when she has her period. And at this point in time, all the hormones are really quite low. So estrogen and progesterone are very low. The brain secretes a hormone called follicle stimulating hormone, and what this is like is it's like fertilizer for a woman's ovaries. Every single woman has a certain number of follicles that are within her ovary at any given point in time. And the follicle stimulating hormone will gently stimulate one of those follicles to become a big dominant follicle. So I want you to imagine that in actual fact, the little follicles sitting on an ovary are in actual fact seedling sitting in a little flower box. And think about that FSH, the follicle stimulating hormone, coming from the brain as if it is fertilizer for those little seedlings.

So what happens is the FSH or the fertilizer slowly increases during the first part of the menstrual cycle, from day one to approximately day 14. And that fertilizer gently stimulates one of the little seedlings to become a big beautiful sunflower. Now it'll block out the sunlight of the other little seedlings, and therefore you only ever get one seedling a month.

Now in nature, in terms of your ovaries, the same thing happens. Follicle stimulating hormone gently increases during the menstrual cycle. It causes one of the follicles to become bigger and bigger and bigger. And through the process of hormones, it suppresses the growth of the other little follicles. And so ultimately, a woman will have one large follicle that it will eventually break open, just like an egg opening, releasing the egg... Or an egg shell opening, rather... Releasing the egg so that it can go down the fallopian tube.

Now, often that's done around day 14, and most women will know that you can also purchase from the pharmacy, or alternatively from a supermarket, ovulation kit tests. These test for a hormone called luteinizing hormone, which surges or starts to increase in the day preceding your ovulation. And what it does is it causes that egg shell to rupture and allow the little egg to be released from the ovary, so that eventually it goes down the fallopian tube.

Now, during this period of time, women may also find that their cervical mucus becomes quite stringy and, in other cases, because the egg shell has opened up releasing a little bit of fluid, they might also notice a little bit of pain, particularly in the ovary where the egg's been released.

From there, within 24 hours, that egg needs to be fertilised. So it's really important that during what we term our fertility window, that you're having sex in order to maximise the chances of pregnancy.

Now, once that egg is subsequently fertilised, then it'll go down the fallopian tube and head into the uterus where it subsequently implants.

In the absence of an egg being fertilised, then a woman will anticipate a period some two weeks later. So where the egg shell actually opens up and releases the egg, the rest of the egg shell collapses on itself forming something called a corpus luteum, and that produces progestogen, which is the major hormone that drives the rest of the menstrual cycle from day 14 through to around about day 28.

Now, just as something is happening in the ovaries, another processes also happening within the uterus. And the uterus is very dependent on the hormones that are being produced within the ovaries to maintain an adequate environment suitable for pregnancy.

So the first part of our cycle from day one to day 14 has a whole amount of estrogen that's being produced from that large, big follicle that's within the ovary. Now, that estrogen is a little bit like watering the grass on the surface of the MCG. So if you imagine the MCG and you imagine the grass growing during the first part of the 14 days of the menstrual cycle, that grass grows. And if you think of the embryo as the beach volleyball, the big volleyball that's been thrown around the MCG as all the patrons at the mcg do the Mexican wave, and you think about that little beach ball then nestling into the grass.

So during the first part of the menstrual cycle, the lining of the womb gets really nice and thick. Once ovulation that egg, or that beach ball, wants to land in the grass or the thickened endometrium of the lining of the womb. Now, if you are pregnant, then of course, the progestogen continues to support that little embryo, and support the grass that's growing or the lining of the womb becoming nice and thick.

And in the absence of becoming pregnant, then all the hormones, both the estrogen and the progestogen which are the major hormones in the latter part of the cycle, drop. And as a result, it's a little bit like cutting the grass off the surface of the MCG. And this is when a woman will experience a period.

So whilst the ovaries and the uterus are two separate organs, in actual fact, they are intimately related, I suppose, when it comes to conception. We need, in the first part of the cycle, the ovary to grow a follicle, produce a huge amount of estrogen, which then subsequently stimulates the uterus to grow or the lining of the womb of the uterus to thicken up and grow in preparation for pregnancy. Once you ovulate, then the ovary produces a whole amount of progestogen to support a pregnancy. And that little egg then moves down into the fallopian tube, into the uterus to implant.

And then if you are pregnant, the little pregnancy hormone that's produced called HCG continues to stimulate the ovaries to produce progestogen and to stop you from having a period so that that embryo can continue to nestle in, implant, and of course, develop into a baby.

So understanding our menstrual cycle is particularly important. For some women, the menstrual cycle may not be 28 days, and a bit may be 35 days or even longer. And so it's really important, at that point in time, to realize that when you are ovulating is generally 14 days before you would expect a period. So for a woman who's having regular 35 day cycles, then ovulation, generally speaking, occurs around day 21. In my opinion, if you're ovulating any more than 35 days, then you really.. Or sorry, you're having a period more than 35 days, you really should be seeing a fertility specialist so that we can give you medication in order to stimulate the ovaries and allow ovulation to occur in a more frequent manner. This doesn't mean IVF. This basically means ovulation induction, where we still are timing sexual intercourse around ovulation.

So, when's the best time to conceive? Well, the best time to conceive as around ovulation, as I've stated before. And so for a woman who's having a regular 28 day cycle, that's day 14. So I tend to say to patients and to couples to have sex every second day through from day 10 through to day 20, realizing that sperm normally stays in the genital tract of a woman for approximately two to three days. So that means if you ovulate a little bit earlier, or a little bit later, there should still be sperm up in the tubes for fertilization to occur.

Of course, as I said before, if you're having a 35 day cycle, then of course, ovulation is occurring day 21. And so you should really be having sex then from day 15 through to day 25 to cover off the same fertility window.

So I hope that goes in part to explaining what a natural cycle is, when's the best time to conceive, and how and what are the requirements to conception.

To refresh, sex timed around ovulation, having healthy sperm, a receptive uterus with no impediments to pregnancy, ovulating, and of course, having open tubes. And the last thing is P for patience. As you commence your fertility journey, it's important to remember that the chances of pregnancy are around 20% per month. As a young woman less than the age of 35, I'd suggest that you do this for approximately a year before considering help from a GP or specialist. And alternatively, if you're over the age of 35, then please see a doctor a lot earlier at around the age of 36... Sorry, at six months.

However, the most important thing is if at any point in time you feel that your fertility is compromised by any one of the factors that I spoke to before; ie- not having enough sex, you're worried about your partner's sperm, the uterus in terms of bleeding may be heavy or alternatively painful, or alternatively, you've had any history of sexually transmitted infections where there may be a concern about blocked tubes, and indeed you're not ovulating frequently, then seek the advice of a fertility specialist much earlier than one year and much earlier than six months for a woman over the age of 35.

I hope you enjoyed this video about your natural cycle and when's the best time to conceive. We've got a whole bunch of other videos on fertility. So if you want to listen to them more, please click on the subscribe button, or alternatively, leave a comment below.

It's really important to take control of your fertility health. So if you need to please contact us at Melbourne IVF and make an appointment with any one of our fertility specialists.

*All opinions expressed on the Fertile Minds YouTube Channel belong to the individual doctors, scientists and specialists, not the Virtus Health group.