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The menstrual cycle explained

4 July 2019

If you’re trying to get pregnant – and you’ve been trying for a while – you’ll know all about the importance of tracking your ovulation and understanding your menstrual cycle hormones.

But ovulation is just one of the menstrual cycle phases – and if you want to be able to pinpoint the precise date of ovulation in advance, it helps to understand the cycle as a whole.

If you're wondering how long the average how long is a menstrual cycle is, this article dives into the details you need to know and shows you what the important signs to watch out for are when it comes to your fertility.

But before getting started, let’s discuss something that’s on a lot of message boards at the moment: cervical mucus.

Why is cervical mucus important – and what can it tell you about your cycle?

Cervical mucus is fluid that’s released by the cervix into your vagina – and this mucus changes in consistency and volume throughout your menstrual cycle:

  • After ovulation, your cervical mucus will be sticky and thick – to stop sperm (and anything else) from getting in.
  • It will then go through other stages of consistency – dry/sticky, then creamy, then wet and watery – until it has the consistency and colour of raw egg whites (slippery, stretchy, clear/white).
  • When it has this “egg white” consistency, it’s known as “egg white cervical mucus” (or EWCM), and it means ovulation is approaching. EWCM helps sperm swim up into the uterus, and it also protects the sperm from the acidic conditions of your vagina.


Checking your cervical mucus for signs of impending ovulation isn’t fail-safe, of course – and some women feel a bit squeamish about touching their vaginal discharge every day. But you might find it useful (and interesting!) to check for EWCM while also using ovulation predictor tests.

What is the menstrual cycle?

The rise and fall of estrogen are what makes the menstrual cycle happen. This is a natural change that occurs in the female reproductive system. The menstrual cycle happens in order to produce oocytes and prepare the uterus for a potential pregnancy.

The menstrual cycle varies from woman to woman and from cycle to cycle: it’s unlikely that your own cycle will be exactly like the one outlined below. By understanding the order of events and why they happen, you’ll be better able to understand your own cycle and pinpoint the best time to conceive.

How long is the menstrual cycle?

It would be odd if all women ran on 28-day cycles, and all ovulated on day 14. Such regularity is in fact highly irregular -  just  *12% of women have a 28-day cycle. Your cycle starts on the first day of your period and starts again on the first day of your next period. Cycles can range anywhere from 21 days - 40 days and that's totally normal.

The menstrual cycle phases 


Days 1–5(ish): you get your period

Day 1 of your period is also Day 1 of your menstrual cycle, and it’s when your uterus sheds the lining that had built up during your last menstrual cycle. (More on this shortly.)

Days 6–12(ish): follicles grow inside your ovaries


Each of your ovaries contains hundreds of thousands of follicles – and about 90% of those follicles contain an egg. (The other follicles are empty.)

Every cycle, a proportion of these follicles (and the eggs inside them) start growing and developing in response to the release of a hormone called follicle-stimulating hormone (FSH) by the pituitary gland. At around the same time, the cells surrounding the eggs produce another hormone: oestradiol, which is a type of oestrogen. This thickens up the lining of the uterus to prepare it for (hopefully) receiving a fertilised egg.

Up to this point, many follicles have been growing and developing at the same time. But then one follicle will start to grow faster than all the others; it’s known as the “dominant follicle” and the cells inside it will produce lots more oestradiol. In response, the pituitary gland stops releasing so much FSH, which has the effect of quieting all the other follicles while the dominant one contains to grow.

Once the dominant follicle (and therefore the egg) has grown to its optimal size, it’s ready for ovulation.

Day 13(ish): LH surge

Your oestradiol levels have been rising all this time and will be at their highest when your egg is “mature” and ready. This acts as a sign to the pituitary gland that everything is in place for ovulation.

The pituitary gland responds by sending out a large amount of a hormone called “luteinising hormone” (LH) – which in turn acts as a signal to the ovary that it’s time to release the egg. This is known as the “LH surge”, and it’s extremely important for detecting the best time to try to conceive.


Day 14(ish): Ovulation

Ovulation normally occurs 24 to 36 hours after the LH surge: the egg breaks away from its follicle and travels from the ovary to the fallopian tube – ready to be fertilised by sperm swimming towards it. This is the specific point at which you’re ovulating.

Once you’ve ovulated, the egg only lives for about 12 to 24 hours. Sperm, on the other hand, can survive for about three days – so they ideally need to be ready and waiting inside the fallopian tubes just before you ovulate.

That’s why it’s so important to know when your LH surge is happening: you’ll be able to time intercourse so that sperm are in the exact place they need to be before you ovulate.

Most other over-the-counter ovulation predictor tests work by trying to detect the LH surge, and they do a good enough job – if you’re one of the 33% of women who have “regular” LH levels, that is. But if you’ve used these kits in the past and are still struggling to conceive, you might want to give the myLotus Fertility monitor a try: it’s the only home-based kit with results equivalent to those from lab-based testing.

How to count your menstrual cycle to get pregnant

Tracking your luteinising hormone levels are a key way to count your menstrual cycle to get pregnant. A considerable two-thirds of women have LH base levels that are above or below the “normal” range – and as a result, their “surge” (or “peak”) levels are also often higher or lower. This isn’t usually anything to worry about: your LH peak is still a peak for you, and you’ll (usually) ovulate afterwards.

Regular at-home ovulation tests define an LH surge within a very narrow range of what’s considered “normal” – and they give you a simplistic “yes/no” (or smiley/non-smiley face) result. If you have low base levels of LH and therefore a low peak, these regular ovulation tests won’t be able to detect your LH peak – and they’ll likely give you a false negative. If you have high base levels of LH, regular ovulation tests will often give you a false positive – regardless of when you use it in your cycle.


The myLotus personalised fertility tracker is different: you use it every day of your cycle and track your LH levels throughout the month. Unlike traditional tests, you actually see your LH levels presented as a number (not a “yes/no” or smiley/non-smile face) – so it’s possible to detect when those levels are rising. This means myLotus can also be used if you’re taking stimulating hormones like Clomid.

For various reasons, some women will have more than one LH surge each month – but in almost all cases, ovulation will only happen after the final surge. Other tests can’t track these things; myLotus can.

You don’t need to be a fertility expert to understand the results or figure out when you’re definitely “surging”: the myLotus app (which is free and connects to the myLotus Fertility monitor) will do all that for you. What’s more, after the first month, it will learn your personalised hormone profile and can provide forecasts for when your next LH surge will be.

Days 15–28(ish): fertilisation (or not)

If the egg is fertilised by sperm, it will travel down the fallopian tube and embed itself in the uterus lining that’s been building up all this time.


A hormone called human chorionic gonadotropin (hCG) is then released, which instructs the ovaries to produce yet another hormone: progesterone. This progesterone takes over the role of oestradiol in keeping the uterus lining thick and nourished while the embryo grows. Your oestradiol/oestrogen and progesterone levels remain high throughout your pregnancy.

If you’ve used a pregnancy test before, you might know that it works by measuring levels of hCG – which is detectable in your urine about two weeks after an egg is fertilised by sperm. (Your doctor can also do a pregnancy blood test, where hCG levels can be detected around eight days after conception.)

Men and non-pregnant women don’t have detectable levels of hCG in their bodies, which is why it makes for a useful pregnancy test. The myLotus Fertility Monitor can detect pregnancy too: all you need to do is check it daily to see if it asks you to do an hCG test (which comes with the kit). This usually happens about 12 days after an LH surge has been detected.

If the egg doesn’t get fertilised, it will disintegrate in your uterus. Your oestradiol and progesterone levels will drop at the same time, and the lining of your uterus will break down. Your period will arrive about two weeks later.


How does age affect fertility?

The myLotus fertility tracker will tell you a lot about your menstrual cycle, but it can’t tell you about the quality or quantity of your eggs – which are both affected by age. If you’re worried about your age in relation to fertility, this article contains a good summary of everything you need to know and talk to your doctor about.

Understanding your body will improve your chances of getting pregnant

Understanding the menstrual cycle is your first step to a better chance of conceiving. Your next step? To understand your own cycle – particularly your LH levels and LH surge. Ovulation predictor test can help with that.

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