Knowing Your Body; Understanding Your Menstrual Cycle And Fertile Window

My latest book, Your Fertile Years, will be out in April, published by Sheldon Press and is available for pre-order on Amazon.

I have made a short video to explain why I wrote the book and what the chapters are about. Over the next 12 weeks, I am going to talk about a different chapter each week, which will include a blog posted on Global Women Connected, a video on my YouTube channel, and social media events.

Chapter 1 is called Knowing Your Body; Understanding Your Menstrual Cycle And Fertile Window and you can watch the video here. In this blog I am going to outline some of the key messages from this chapter.

Your anatomy

The female reproductive system is made up of two ovaries, two fallopian tubes, a womb, cervix (neck of the womb), vagina, and the vulva (external genitalia).

The term vagina is often used incorrectly. Vagina only refers to the muscular tube leading from the external genitals (genitalia) to the cervix of the womb (uterus). Most people use vagina to refer to the woman’s external genitalia, which are actually called the vulva.

The vulva is made up of the clitoris, urethra (which leads to the bladder and allows for the passage of urine), and the labia majora and labia minora (these are the fleshy lips of the vulva). Women have three openings: the urethra for urine, the vagina for menstrual blood, intercourse and delivery of the baby, and the anus for faeces.

I have written before about vaginal spas. What do you think about these procedures? Would you let someone steam your vulva and vagina?

The menstrual cycle

Women have menstrual cycles for about 40 years of their lives. The two key events of our menstrual cycle are having a period and ovulating.

The textbook menstrual cycle is 28 days, but anything between days 21 and 35 is normal. If a cycle is shorter than 21 days or longer than 35 days, there could be issues with fertility and the woman may want to see her doctor if she is trying to get pregnant.

The first day of the menstrual bleed is counted as day 1 of the cycle. The first half of the menstrual cycle is called the follicular phase and this is when the egg is maturing and ready for ovulation. The two weeks after ovulation are called the luteal phase. This is when the womb is preparing for implantation of the embryo.

The menstrual cycle is controlled by hormones which rise and fall at different times. The key hormones are gonadotropin releasing hormone (GnRH) which stimulates the production of two key hormones: follicle stimulating hormone (FSH) and luteinizing hormone (LH). Oestrogen is produced by the growing follicle which contains the egg. And progesterone prepares the womb for the implanting embryo.

Periods – normal and abnormal

Worldwide, about 800 million women are having their period right now.

Menstruation is caused by the shedding of the womb lining when a pregnancy does not occur and our body starts a new cycle. A period can last for 3–7 days but this varies between women. In 2019 I did a study with the app Natural Cycles and we looked at over 600,000 menstrual cycles. We found the average period length was 3.8 days.

During a period, women usually shed up to 80mls of blood, but it is usually only about 6-8 teaspoons (30-40ml). A period pad or tampon should be changed every 3-4 hours.

Some women have very heavy periods, shedding over 80mls of blood. Heavy periods (menorrhagia) can impact negatively on their life. ‘Flooding’ is the term used to describe the situation where normal period products are not sufficient and double protection and frequent changing is required, more than every 3-4 hours.

Most women experience some pain during periods (dysmenorrhea) with 15% classing the pain as severe. The pain tends to improve with age and after childbirth.

Some women have no periods, which is called amenorrhoea. Primary amenorrhoea is when periods have not started by the age of 16 and secondary amenorrhoea is where a woman had periods, but they stopped. If you are not having periods you are not ovulating and will be infertile.

I recently did a podcast about periods – listen here.

Ovulation

At ovulation, the egg is released from the follicle and it is wafted into the fallopian tube. If it meets a sperm, it might fertilise to make an embryo, which will travel to the womb where it will try to implant.

Textbooks tell us that ovulation takes place around day 14. But the day of ovulation varies depending on how long the cycle is. In our study with Natural Cycles, we found the average day of ovulation was day 17 but this ranged from day 10 to day 26 depending on the cycle length. As expected, women with shorter cycles ovulated earlier, and those with longer cycles ovulated later.

Fertile window

The fertile window is when women are most fertile and can fall pregnant. It is important for women to understand when their fertile window is, whether they are trying to become pregnant or not.

Unless they are using hormonal contraception, most women will ovulate every month, but as women age, they will have more cycles where they do not ovulate, called anovulation, which decreases their fertility.

Pregnancy is only possible if you have sex during the five days before ovulation or on the day of ovulation. This is because the egg is only viable for 24 hours, so 24 hours after ovulation, the fertile window is closed. However, the fertile window includes five days before ovulation because sperm can survive in the female genital tract for up to five days. So, if a woman has unprotected intercourse on day 10 of her cycle, but does not ovulate until day 15, she can become pregnant because the sperm may still be alive. The most fertile days are the three days leading up to ovulation.

In my study with Natural Cycles we found that on average ovulation happened on day 17, but some women ovulated as early as day 10 and as late as day 26.

There are methods to determine when ovulation occurs. They are called Fertility Awareness-Based Methods (FABM) and include monitoring menstrual cycle dates which is called the calendar method; measuring basal body temperature; observing changes in cervical mucus through the cycle or the Symptothermal Method (calendar, cervical mucus and basal body temperature measurements combined). Ovulation can also be monitored using the detection of hormones in the urine, usually LH, sometimes in combination with oestrogen.

This has been a whistlestop tour of chapter 1 of my book.  I would love to hear from you – did you learn anything reading this blog – any questions?

Next week I will tell you about chapter 2 – female fertility decline.