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Before I started properly tracking my menstrual cycle, I had a number of late period freak-outs. Usually resulting in me awkwardly buying an unnecessary pregnancy test at the supermarket, only for my period to arrive a few days later.
Has this ever happened to you?
Late Period or Late Ovulation?
I later learnt that my period was never late, I had just ovulated late. If I had been tracking my cycle and observing the signs from my body, I would have been able to identify when I ovulated. If ovulation was later in my cycle than usual I would have known to expect my period later.
It is far more useful to understand what is happening in real time in your menstrual cycle, rather than subscribing to the belief that all menstrual cycles are 28 days long.
The phases of the menstrual cycle
Our menstrual cycle has two phases:
1. The Follicular phase – from menstruation to ovulation we are in the follicular phase (pre-ovulatory phase);
2. The Luteal Phase – from ovulation to the start of the next menstruation we are in the luteal phase (post-ovulatory phase).
Here’s a helpful visual of the phases that I posted on Instagram:
length of the Follicular Phase
The length of the follicular phase, or pre-ovulatory phase, is variable as it depends on when ovulation occurs. Ovulation is a fluid event and doesn’t always happen in the middle of the cycle. It might, but the timing of it can change from person to person, and cycle to cycle.
Your follicular phase will be as long as it takes your body to ovulate in that cycle.
Even though you may have heard menstrual cycles often referenced as being 28 days long, with ovulation occurring on Day 14, this is simply not the case for everyone. It’s just an average. In fact, a 2019 study of 600,000 menstrual cycles found that just 13% of menstrual cycles were 28 days long.
It’s common to have cycles that are longer or shorter than 28 days and ovulation can occur at different times. Take it from me, I often ovulate around Day 21 of my cycle or sometimes even later!
The timing of ovulation can also be impacted by things like stress, illness, hormonal imbalance and medical conditions.
Even if you have historically ovulated at the same time every cycle, a real-life event could impact the timing of your ovulation. That’s why it is so important to track ovulation in real-time rather than rely on an app that uses an algorithm based on past cycles to make predictions.
Length of the Luteal Phase
The length of your luteal phase, or post-ovulatory phase, is much more predictable. Once you ovulate, your luteal phase won’t be any longer than 16 days (unless you’re pregnant). The luteal phase can vary from 10 – 16 days in length, but is typically around 2 weeks.
This means, once you confirm ovulation, you will know that your next period will arrive within the next 16 days (unless you’re pregnant!).
Another great benefit of tracking ovulation – an approximately two week notice of when your next period will arrive!
How to Know When You Ovulate
Confirming ovulation can be done fairly simply by tracking your basal body temperature (BBT) using a basic digital ovulation thermometer. You can get one for pretty cheap at your local drug store or online.
Once you have the correct thermometer, you need to take your temperature every morning when you wake up and chart it on a graph. You can do this on a paper chart with a pencil. Or you can use an app like Read Your Body or Kindara.
If you don’t want to take your temperature each morning, you might want to get a Tempdrop. Tempdrop is a wearable temperature sensor that you wear on your arm overnight and it calculates your temperature automatically for you. It makes charting your BBT so much easier and I personally use and love it. You can learn more about Tempdrop here and if you decide to get a Tempdrop you can use my code TDBETTER10 for a 10% discount.
For 10% off Tempdrop use the code TDBETTER10
Once your temperature rises and stays risen, you will know that you ovulated. Once you have ovulated you will move into the Luteal Phase of the cycle, and this phase will always be a similar length for you, somewhere around 10 – 16 days, no longer.
The temperatures on a chart will look something like this:
An Important Note on Temperature
Basal Body Temperature (BBT) is a retrospective indicator of fertility. We can only confirm ovulation using BBT after the fact. By the time we see the temperature rise, ovulation has already occurred. For this reason, you cannot rely on tracking BBT on its own for the purpose of avoiding pregnancy, nor for the purpose of when to time intercourse for achieving pregnancy. The best time to have intercourse if you are wanting to fall pregnant is in the lead up to ovulation – before the temperature rise.
Ovulation happens at the end of the fertile window. The fertile window opens up to 5-6 days prior to ovulation because we start to produce cervical fluid which can keep sperm alive inside for 3-5 days.
Let’s take a look at what’s going on in the follicular phase and luteal phase in more depth.
What is happening in the Follicular Phase
The Follicular Phase of the menstrual cycle is the time from the first day of the period through to ovulation. Part of this phase is the menstruation phase, which is when the bleeding occurs. After the bleed is over, the follicular phase is the time when follicle stimulating hormone (FSH) is released, stimulating the growth of 5-20 follicles.
The developing follicles release a form of oestrogen called estradiol which stimulates the lining of the uterus to grow and thicken. This is preparing for the possible implantation of an egg and subsequent growth of a baby.
The more estradiol produced, the thicker your uterine lining will be and the heavier your period will be, if pregnancy does not occur.
Estradiol is also responsible for the production of cervical fluid. Cervical fluid is produced in the lead up to ovulation and is a sign of fertility. Cervical fluid is designed to keep sperm alive inside the otherwise acidic vagina for up to 5 days. If you want to learn more about fertility signs, you can click this link to read my previous post What is Fertility Awareness.
The follicular phase culminates in one follicle (or two, in rarer instances – this is what causes fraternal twins if conception were to occur) becoming dominant and then finally rupturing and releasing an egg – this is ovulation! Ovulation is triggered by the luteinising hormone (LSH).
“Ovulation is an all-or-nothing event. You cannot sort of ovulate. Your either ovulate or you don’t. Once you have ovulated, there is no going back. Your egg has been released, and it cannot be recalled…after ovulation, you will either be pregnant or you will get your period approximately two weeks later. There is no third option. It’s not possible to ovulate but then not be pregnant or get your period.”Lara Briden – The Period Repair Manual
What is Happening in the Luteal Phase
Once ovulation has occurred, you then move into the luteal phase. Unlike the follicular phase, the luteal phase has a finite time span, dictated by the lifespan of the corpus luteum.
The corpus luteum is an incredible temporary endocrine gland. It forms from the empty follicle left behind from ovulation.
The corpus luteum produces the very beneficial hormone progesterone, which is responsible for nourishing pregnancy, but also holds other benefits not just for a healthy reproduction system and healthy periods. Progesterone is also beneficial for energy, sleep, hair and skin and bones and muscles. You can read more about the superpowers of progesterone in this post by Lara Briden.
If pregnancy were to occur after ovulation, the corpus luteum would stick around, producing progesterone for three months. After this the placenta would take over this job.
If pregnancy does not occur after ovulation, the corpus luteum will only be around for a short period of time, around ten to sixteen days. After this, it will disintegrate, progesterone levels will drop and the uterine lining will begin to shed. And just like that, the cycle has come full circle and we are back at menstruation.
Interestingly, progesterone causes a rise in basal body temperature, which is why we can use our basal body temperature to identify when we ovulate!
The temperature rises after ovulation and stays in this higher range while the corpus luteum is still producing progesterone. Once the corpus luteum disintegrates and stops producing progesterone, the temperature drops again and the next period starts.
Best Books to Learn More About Your Cycle
If you are interested to learn more about your menstrual cycle, period and how your fertility really works, then I cannot recommend these books enough:
|Period Repair Manual by Lara Briden||Buy on Amazon US|
Buy on Booktopia
|Taking Charge of Your Fertility by Toni Weschler||Buy on Amazon US|
Buy on Booktopia
The key takeaways are:
> while the follicular phase, from menstruation up until ovulation, can vary in length, once ovulation has happened a period will arrive within the next two weeks (unless pregnancy has occurred).
> If you know when you ovulate, you can know when to expect your period.
> Unless pregnant, your period won’t be late. It may be later than expected based on previous cycles but the reason will be due to ovulation being late/delayed. That’s why tracking ovulation is the key to knowing exactly what’s going on in your cycle.
From a practical sense, as an example, this is relevant to me at the moment because I’m currently on Day 25 of my cycle and I haven’t yet confirmed ovulation! If I wasn’t tracking my cycle, I’d be expecting my period to arrive within the next week and when it didn’t I’d be freaking out and probably off to waste money on a pregnancy test.
Since I know I haven’t ovulated yet, I’ll be cool as a cucumber when my period doesn’t arrive next week.
If you liked this article, you may also be interested in these:
Keep in Touch
Have any questions? Please leave a comment below, email me or DM on Instagram @thebetterperiod_
1. Period Repair Manual: Every Woman’s Guide to Better Periods – by Lara Briden;
2. All about the follicular phase of the menstrual cycle https://www.healthline.com/health/womens-health/follicular-phase
The Better Period
Ellie Heasman is a period blogger and founder of The Better Period. Ellie helps people on their journey to a better period through introducing them to the world of menstrual cups and period underwear, and sharing knowledge about the menstrual cycle and fertility awareness. You can join in the better period conversations on Instagram @thebetterperiod_ or find out more about Ellie here.