The menstrual cycle; a phenomenon experienced by approximately 50% of the worlds population; yet a phenomenon fraught with myth, taboo, confusion and misunderstanding. Did you know that for centuries it was believed that the menstruating woman could sour wine, kill insects, or cause fruit to drop from trees; and menstrual blood believed to be toxic, the female constantly in need of purification, condemning her to be the weaker sex! While we have debunked some of the myth and are moving toward normalising menstruation, there still seems to be some confusion around the cyclical nature that is womanhood (which I touched on briefly here). So I thought I’d shed some light…
It is believed that we ladies are born with around one million oocytes or eggs, and by the time we reach menarche (our first period) we have approximately 300,000. This perpetuates an idea that we are born with a certain amount of eggs that will eventually run out. However, there is new and very exciting evidence to suggest that the ovaries contain stem cells that create new eggs month to month, and this can go on indefinitely (1,2)!
The average Australian woman reaches menarche around the ages of 12 to 13 and can expect to menstruate with relative regularity until around the ages of 45 to 50. That’s between 30 and 40 years of menstruation, averaging 360 to 400 periods across our lifetimes! The average length of the menstrual cycle varies from woman to women and is dependent on a number of factors including stress levels, weight balance, exercise levels and diet. 28 days is generally considered ‘normal’, however anything between 21 and 35 days is healthy.
The menstrual cycle is governed by the interplay between various reproductive hormones managed by our brain, ovaries and uterus. There are three phases of the menstrual cycle – the follicular phase, ovulation, and the luteal phase – and it is varying levels of these reproductive hormones that differentiate these phases and initiate the flow from one phase to next.
Lets take a look at these phases and their associated hormones in further detail.
The follicular phase:
Day one of your menstrual cycle is the first day of your period. A period lasts on average between 3 and 5 days (this does not include pre- or post-menstrual spotting – that’s the scanty stuff at the beginning and end). Menstrual discharge does not only contain blood but also endometrial tissue, cervical and vaginal secretions. It is normal to lose about 50ml of fluid during your period, and anything more than 80ml would be considered heavy. It can be a bit tricky to know exactly how much you are losing, but it’s helpful to note that one “regular” pad or tampon holds about 5ml of fluid, and a “super” pad or tampon holds about 10ml. Add this up across your period and you’ll have a pretty good estimation of how much fluid you’re losing.
During your period oestrogen levels are low. This signals your brain to secrete follicle-stimulating hormone (FSH), which as its name suggests stimulates the growth of around 20 follicles within the ovaries. As they grow, the follicles begin releasing oestrogen and this signals to the wall of the uterus to begin thickening. At around day 8 of your cycle one of the follicles has become dominant. Oestrodial (a type of oestrogen) levels start to rise. At around this time of the cycle your body is gearing up to potentially make a baby. Oestrodial is a feel good (or feel sexy) kind of hormone that increases mood, energy, libido and vaginal lubrication. It’s helping get you in the mood to fertilise that egg!
The rising levels of oestrodial trigger a surge in luteinising hormone (LH). This triggers that dominant follicle to rupture and release its egg, and this occurs on or around day 14. You might feel a slight twinge of pain on one side of your lower pelvis as this occurs.
The luteal phase:
Ovulation is followed by the luteal phase, where the corpus luteum (or the now empty ovarian follicle) secretes greater and greater levels of the hormone progesterone, and reduced levels of LH. Progesterone literally means “pro-gestation” and its job at this stage is to tell the uterus to thin out and mature so that a fertilised egg can implant there. As progesterone increases, oestrogen drops and levels out. If fertilisation were to occur, the embryo would travel through the fallopian tube and implant in the prepared uterine wall. At this point human chorionic gonadotropin (hCG) is released, signalling the corpus luteum to continue to secrete progesterone. Increased levels of hCG are what indicate pregnancy on a pregnancy test. The continued secretion of progesterone tells the body to hold on to the fertilised egg. If conception does not occur the corpus luteum will breakdown over the next 14 or so days. Progesterone levels fall which stimulates the shedding of the uterine wall, you get your period and the cycle starts all over again!
Pretty magical stuff right? The female body is truly wondrous. I think it’s so important that we understand what is going on inside our bodies so that we might be informed and empowered; and embrace the beautiful cyclic nature that is being a woman! And I hope this post helps you along the way to doing just that.
If you have any questions or comments I’d love to hear from you! Please email me or get in touch via the comments section below.
(1) White, Y.A., Woods, D.C., Takai, Y., Ishihara, O., Seki, H. & Tilly, J.L. (2012). Oocyte formation by mitotically active germ cells purified from ovaries of reproductive age women. Nature Medicine, 18(3), 413-421.
(2) Ding, X., Liu, G., Xu, B., Wu, C., Hui, N., Wang, J., Du, M., Teng, X. & Wu, J. (2016). Human GV oocytes generated by mitotically active germ cells obtained from follicular aspirates. Scientific Reports, 6, 1-17.