When Are You Most Fertile?

There is a lot of conflicting information regarding when males and females are most fertile. Common schools of thought simplify fertility by saying that men are capable of pro-creating for their entire lives and women will experience the menopause at the age of 40.

This week LetsGetChecked is here to rifle through the misinformation and discuss the most important aspects of your fertility, which include your age, the timing and your overall hormonal health to definitively answer, when are you most fertile?

LetsGetChecked is joined by Amanda Laird, founder of The Heavy Flow Podcast to discuss all things fertility related, as well as one of the most common causes of infertility in women, polycystic ovary syndrome.


When Are You Most Fertile? - Age



Men have the ability to reproduce from the moment sperm production begins. This generally occurs during puberty. Puberty in males begins between the ages of 9.5 and 14. Among some of the most common signs of puberty in young males, you can expect the voice to become deeper, a growth spurt in height and muscle mass, going up a shoe-size, the development of the Adam's apple, the enlargement of the testicles and the growth of body hair.

A study published in Human Reproduction found that the average age of fathers is increasing in the U.S by analyzing over 1 million births between 1972 and 2015.

Through analyzing average birth dates and rates, the study concludes that the average age to become a father has steadily increased by 3.5 years in the last forty years.

“In the U.S, the average age to become a father has increased from 27.4 to 30.9 years of age in the last 40 years.”


Women are traditionally known to be capable of reproduction from the onset of menarche. Menarche refers to the first female menstrual cycle. The most common age range to start the menstrual cycle is between 10 and 15 years with the average age of first menstruation being 12 years old.

One study reports that 10% of U.S girls will experience their period before the age of 11, while 90% of all U.S girls will experience menarche by the age of 13.75 years of age. By the age of 30, a woman's chance of conceiving is 20% per month. At the age of 40, this chance is reduced to 5%.

U.S. figures show that women were having their first child at the average age of 24.9 years in 2000. By 2014, the average age had risen to 26.3. In 2016, a study carried out by the CDC revealed that the average age for women to have their first child was 28 years of age, with the prediction that this number will only continue to rise.

"Women in the U.S.A are more likely to have their first child in their early 30s."

When Are You Most Fertile? - Timing



Men do not have a "fertile window" per se as sperm is continually formed and stored in the testes. Healthy sperm is viable anytime under normal health circumstances. Sperm has the ability to live for up to six days in the uterus.

That being said, there are studies (linked below) that show that men are most fertile in the mornings and during winter months.

One study suggests that the volume of sperm found in the testicles is higher in the morning, this is hypothesized for a number of reasons. It is important to remember however that if you have a healthy sperm count, your volume of sperm may only decrease by 1%, and sperm quality is more important than quantity.

Sperm counts may be higher in the morning for a number of reasons, including but not limited to whether you have sex during the day. It is generally agreed that the time that you have sex during the day doesn't significantly impact on your chances of getting pregnant.

Another study suggests that men have a better chance of healthy conception during winter months. The study, carried out by Ben-Gurion University of the Negev tested 6,455 semen samples over a three year period. The findings report that sperm quality is at its highest during winter months. This could be explained by dropping temperatures and the widespread belief that sperm quality may be maintained at lower temperatures against studies that show that sperm quality is less efficient in environments that produce higher temperatures.

This study cross-referenced with another carried out by Soroka Medical Center which showed that there are higher birthrates during autumn which could be connected to higher success rates in conception during winter months. While these studies display decent research, there are no definitive findings that exemplify when sperm may or may not be at its best quality.

If you maintain a healthy lifestyle that includes a balanced diet, regular exercise, and cut down or quit smoking, drinking alcohol or other recreational substances, your likelihood of successful conception is heightened greatly.


Women are most fertile during the ovulation period of their cycle. This “fertile window” refers to the six days between the follicular and luteal phase, these phrases may sound complicated but it refers to the phases in the menstrual cycle where the reproductive system is setting up a "nest" for the egg. These phases are explained in more detail below.


To understand your “fertile window”, it is important to understand what is occurring through each phase of your menstrual cycle. The menstrual cycle occurs in four stages. If you have a twenty eight day period, the below details how the four stages of your period will likely occur. For those who have longer or shorter cycles, this offers a guideline for the stages of your cycle.

Menstrual Phase


(Source: LetsGetChecked Fertility Test Calculator)

Day 1-up to or over 7 days

Menstruation may last from 3 to 7 days and include the expulsion of the thickened endometrium through the vagina. Expelled menstrual fluids include mucus, blood and cells that line the uterus.

Follicular Phase

Day 1-14

The follicular phase begins on day 1 of menstruation and lasts up until ovulation. Follicle Stimulating Hormone (FSH) stimulates the ovary to produce follicles that encapsulate developing eggs.

Ovulation Phase

Day 10-16

During the follicular phase, one follicle will mature while the others die off, this causes a thickening of the lining in the uterus to prepare for the implantation of the egg.

Day 14

Ovulation occurs when the mature egg is released from the surface of the ovary. This usually occurs two weeks before the menstrual phase. Ovulation is triggered by high levels of luteinizing hormone. The egg is moved through the fallopian tube by tiny hair-like projections. When the egg reaches the uterus, it has a 24 hour window to meet a viable sperm, if the egg and sperm do not fuse, the egg will die.

Luteal Phase

Day 16-28

During ovulation, the egg is released from the follicle that develops during the follicular phase. The follicle remains on the surface of the ovary while the ovary is transported to the uterus during the luteal phase, the follicle develops into the corpus luteum, which is a structure that releases progesterone, along with small amounts of oestrogen. This release stimulates the  thickening of the uterine lining for the egg to implant once it is met with sperm.

If conception does not occur, the corpus luteum will die, usually on day 22 of your cycle. The drop in your progesterone levels stimulates the degeneration of the uterine lining, also known as menstruation and the cycle begins again.

When are you most fertile? - Hormonal Health



In the largest scale study known to date that examines male fertility, researchers collected semen samples from 42,935 men from 50 countries between 1973 and 2011 in an attempt to measure sperm quality and quantity.


(Infographic Source: Big Think)

The results showed a somewhat drastic decline of 59.3% of total sperm count within the sample group over the 38 years. In North America, Europe and New Zealand combined, there was a 52.4% decline in total sperm per milliliter of semen.

Taking the global study into mind, it is also important to note that biologically, male sperm count is said to start declining at the age of 20, this process then begins to speed up noticeably by the age of 40 years of age. Andropause is not as widely known as the menopause and it isn’t necessarily considered to be an equivalent to the menopause, as andropause is a much more subtly and over a longer period of time.

The symptoms of andropause are not similar to that of the menopause which include hot flashes and a cessation of certain regular physiological processes that occur during the menstrual cycle.

An emerging school of thought hypothesizes that global male fertility is beginning to suffer by cause of modern lifestyles that have resulted in the quality and quantity of sperm counts decreasing.

As men age, levels of testosterone may also decline, which could explain symptoms ranging from fatigue to mood-swings.


The most common cause of infertility in women is a failure to ovulate. 40% of women with infertility issues have difficulty ovulating.

Primary Ovarian Insufficiency (POI) and Polycystic Ovary Syndrome (PCOS) are the two most common causes of infertility in women by ovulation failure. Endocrine disorders such as thyroid diseases, pituitary gland and/or hypothalamus disorders may also cause hormone-imbalancing ovulation disorders. Ageing and lifestyle factors are significant factors that play a part in women's failure to ovulate.

Polycystic Ovary Syndrome (PCOS) is the one of most common endocrine disorder experienced by women. PCOS occurs when women produce a higher than normal volume of male hormones. Imbalanced hormones may cause infertility and metabolic issues.

PCOS affects 10% of women who are of a child-bearing age.

Symptoms of PCOS may include:

  • Inability to become pregnant
  • Irregular periods or total absence of periods
  • Excessive hair growth on the buttocks, chest or face
  • Weight gain
  • Hair thinning
  • Acne
  • Oily skin

Living With Polycystic Ovary Syndrome: Amanda Laird


Amanda Laird is a writer, registered holistic nutritionist and the founder of The Heavy Flow Podcast. Laird strives to open up conversations on menstruation, fertility, pregnancy, menopause, contraception, mental health and sexuality through a political and feminist view-point. The podcasts revolve around topics that have traditionally been viewed as something that should be kept quiet. The Heavy Flow podcast is for women by women. This week, LetsGetChecked is joined by Amanda to discuss female hormonal health, as well as her own personal experience of living with polycystic ovary syndrome.

What is the goal of The Heavy Flow podcast?

My goal with the Heavy Flow podcast is to talk and have conversations about what we’ve been told we’re not allowed to talk about. So many pregnancies end in miscarriage and so many pregnancies end in abortions and yet none of us want to have an open and honest conversation about these issues. By having these conversations, I’m trying to normalize talking about your period. The goal of the Heavy Flow podcast is educating and normalizing.

How did the Heavy Flow podcast get started?

I noticed a consistent connection between my clients, their diets and their menstrual health. You go to the doctor and they ask you when was your last period. If you have symptoms of low energy, or you’re just trying to lose those last few pounds, you can bet that there is a connection between those symptoms and your last period, especially if you are experiencing irregular, heavy or painful periods.
I noticed that my clients and I would spend the whole session discussing hormones, fertility and cysts. There was barely any time to discuss the food part of their nutrition!  I kept wondering “Why don’t my clients understand their bodies?” I think it comes down to gender bias, medical bias and the literature that is widely available to us. The Heavy Flow Podcast acts as a way to start talking about these important things.

Do you still think there is a stigma attached to discussing female reproductive health?
Absolutely. I live in my “period body”, I am one of those people who talks about these issues all the time. A couple of years ago, I wasn’t being interviewed about hormonal health, today I am. The conversation is changing but we still have a way to go.

“Abortion, sex, miscarriage and periods are topics that people don’t want to discuss. How did we get here?”

Why do you think this is?

Historically, a menstruating body was a really startling image.  Mysticism and fear related to menstruation have been ingrained for centuries. Female bodies have been feared, misunderstood and completely ignored.

It’s a vicious cycle. If you don’t understand something, you fear it.

In earlier days, it was theorized that menstruation was linked to animals that bled when they were in heat. It was soon believed that women were in heat when they were bleeding, which is quite ironic. This could reinforce the taboo that exists around periods, especially around having sex while on your period.

Quick Fire Hormones

For many of us, there may be a certain air of confusion surrounding hormones, because of the medical jargon attached to the words used to describe hormonal health. If you could the rephrase the most common female hormones, as if you were describing them to your friends. How would you?


Progesterone is the “superhero hormone”. Progesterone is actually the most underrated hormone because estrogen gets all the press. We produce it in the second half of our cycle. Progesterone is the glue that holds the uterine lining together. It also combats breast cancer, thyroid inflammation, and stress.

Follicle Stimulating Hormone

Follicle Stimulating Hormone does exactly what it says on the tin. Follicle Stimulating Hormone stimulates the ovaries, allowing for the release of the egg.

Luteinizing Hormone

Luteinizing Hormone, together with follicle stimulating hormone allows for complete follicular growth of the corpus luteum. Luteinizing Hormone is essential during pregnancy for the production of progesterone in the first trimester.


Prolactin is all in the name. Pro to produce and lactin, indicating lactation. Prolactin generated throughout a woman’s life and menstrual cycle. It stimulates the production of breast milk, suppresses ovulation and is a bio-marker in diagnosing breast cancer.


Oestradiol is one of the most famously known hormones in women’s health with a multitude of functions. It takes part in producing cervical mucus, maturing eggs during ovulation and developing secondary sex characteristics in women during puberty.


True Or False: Hormone Myths Debunked

You have a 25% chance of getting pregnant each month

True & False: It depends. It depends on your age. When you’re in your 20s, 30s, and 40s, these chances vary. It is true to say that it’s not 100% each month and getting pregnant is not as easy as you may think.

If you have a heavy period, it means you’re more fertile

If you have a very light period, it means you’re not very fertile

If you have high levels of testosterone, it’s more likely that you will suffer from PCOS.

If you miss a period, it definitely means your pregnant

If your period becomes irregular, you should panic
False: However, if you do have very irregular or painful periods, you should get it checked out. If you have a very heavy flow, you need to speak with someone to get it checked out.

In your own words, what is PCOS?

PCOS is an endocrine disorder that affects 5-10% of women around the world.

What are the primary symptoms of PCOS?

I was officially diagnosed in 2014 although I had struggled with hormonal imbalance from the time that I was a teenager. PCOS is a collection of symptoms, it varies from person to person but the Rotterdam Criteria state you need to have at least two of these three symptoms to be diagnosed with PCOS: Irregular or anovulatory periods; Elevated levels of androgen (male sex) hormones; and/or polycystic ovaries.

Other symptoms might include acne, fatigue, weight gain, infertility, excessive hair growth, anxiety, depression and low libido, these symptoms may be brought on by other conditions but are commonly associated with PCOS.

How has PCOS affected your life?

I took hormonal birth control for most of teens and throughout my 20's, not just for contraception but to manage my "crazy periods" - they were highly irregular and heavy, long and painful when they did show up.

I no longer take hormonal birth control. I manage my symptoms with nutrition and lifestyle, and from time to time acupuncture, herbs and supplements. Your period is a vital sign that can tell you a lot about your health and wellness and I know when my periods start to become irregular or change in some way it's usually a sign that I'm not taking care of myself and managing my PCOS.

What steps do you take to improve the symptoms associated with PCOS?
I'm a nutritionist, so what and how I eat is always at the centre of my self-care routine. At the same time, I recognize that food isn't the only important factor in the PCOS puzzle. Exercise and, perhaps most importantly, stress management is crucial too. In fact, I'd put stress at the top of the list. It’s proven that stress can negate the effects of a healthy diet. So all the kale salads and green juice in the world aren't going to make a difference if you're stressed out. Putting down my phone, taking a walk, going to yoga or just remembering to take a breath are small ways that I try and keep on top of my daily stress.

As a nutritionist, what would be your main steps to eating optimally for PCOS?

Since PCOS affects your body's insulin response, being mindful of your blood sugar and avoiding spikes and crashes is very important. That means cutting back on sugar (yes, that means even the "healthy kind"!), refined carbohydrates, alcohol and caffeine. Include a little protein and fat with your meals and snacks. This helps to keep your blood sugar stable by slowing down digestion and keeping you fuller for longer. A few of my favorite blood-balancing snacks are an apple with a handful of almonds or a smear of peanut butter on fruit; a hard-boiled egg with veggie sticks or half an avocado with a slice of whole grain toast.

What advice would you give to people who have just found out they have PCOS?

It can be really overwhelming and scary to be diagnosed with a health condition. Whether you've been diagnosed with PCOS or any other health condition, you don't have to do all the things, all at once. Instead of aiming for perfection, focus on making small, sustainable changes one at a time.

"Keeping it simple makes it easier to stick to your new habits and routines, and will add up to big changes before you know it."

Written by Hannah Kingston | Approved by Medical Director Dominic Rowley