Fertility – what they don’t teach us in school

Katherine Maslowski

I don’t know about you, but I left school very confused about my own fertility. There seemed to be two conflicting messages:

  1. In “sex education” the message seemed to be we could get pregnant by just looking at a boy and this needed to be avoided at all costs
  2. In biology, conception was taught as a “miracle of nature” that was so complex that it was amazing anyone ever managed to have a baby without anything going wrong

As a teenager, this was very confusing!

I even spent six years at medical school learning about the human body and it still didn’t do much to improve my understanding! I remember being told in our first year by one of the lecturers that we were never going to be more fertile than we were then. He said that now was the time to go and have babies. Not the most helpful thing to say to a bunch of 18-year-olds who desperately wanted to get into medical school!

Nowadays there is so much information around that it can get confusing to know what to believe. We should all be able to make informed decisions about whether we want children, how many we want and when we want to have them. To do this though we need to understand our own fertility!

So what now?

Unfortunately, there isn’t really anything that will guarantee we will be able to have a baby if we want one. It is all just a matter of statistics and probabilities (and sometimes it just seems like a cruel game). But the more we understand, the more we can try and play the game to our advantage.

I’m going to go through the basics of female fertility so hopefully, it makes a bit more sense. I’ve added some useful resources at the end if you want to find out more and a “too long, didn’t read” section just in case you simply want a summary!

Quick disclaimer:

I am writing my Master’s dissertation on sex and fertility education in secondary schools. I am very passionate about this subject and making sure women are able to make informed choices.

Now, let’s get started.


First some definitions (so we are all on the same page):

Fertility: the ability to conceive children or become pregnant by having sex

Puberty: a set of hormonal and physical changes that mark the transition from childhood to adulthood (and the beginning of the biological ability to have children)

Menopause: the end of a woman’s ability to have children and the associated hormonal and physical changes

Ovulation: when the ovary releases an egg. This usually happens once a month. Without ovulation it is not possible to get pregnant by having sex

Fertilisation: when the egg meets a sperm (usually in the fallopian tube). This is also sometimes called conception and is the beginning of a pregnancy


Does female fertility decline with age?

Yes. Unfortunately, the concept of a “biological clock” isn’t completely made up. As women, we are born with all the eggs we will ever have (as opposed to men who start making sperm during puberty and then continue throughout their life). Women are theoretically “fertile” between puberty and menopause. There are lots of factors that can affect this. The general rule is that it gets harder to get pregnant as we age, particularly after our late 30s.


Generally speaking, our fertility reduces slightly between our late 20s and early 30s. There is a bigger drop in our late 30s. Most women are no longer fertile by the age of about 45. This is several years before the average age of menopause (the average age is 51 in developed countries). BUT this doesn’t mean that everyone in their early 20s can easily have a baby and no women in their 40s can get pregnant naturally. This is all just based on population statistics and averages.


It is important to know this to let us make informed choices. For example, if you want to have six children it might not be such a good idea to wait until your mid-30s to get started. Everyone has different goals about whether they want a family at all, and if they do, what size/kind of family they want. To make decisions and avoid the heartbreak of missing out on having children I think we all need to understand the basics of fertility.


This table has come from a study that looked at when couples should start their family if they have plans for 1, 2 or 3 children. The table looks scary at first, but it is just to give an idea of how easy (or difficult) it might be to have a certain number of children at various ages.

Source: Habbema et al. (2015)

When is the best time to have sex if I’m trying to get pregnant?

The best advice for people trying to get pregnant is to have “regular” sex. This usually means every 2-3 days, but it is best to do whatever works best for you and your partner. Trying to have a baby can be a very stressful process and trying to time sex at certain moments within your cycle can just add to the stress.


This being said, it is only possible to get pregnant around the time of ovulation (when the egg is released from the ovary). The egg is released from the ovary and then lives for between 24-48 hours. Sperm live can live for up to 7 days within the vagina/uterus/fallopian tubes. Essentially, there needs to be sperm around when you ovulate if you want to get pregnant (and the opposite if you don’t want to get pregnant).


Working out when you ovulate requires a basic understanding of the menstrual cycle flow. This is the cycle of hormones within your body that controls your periods.


The menstrual cycle and fertility

The menstrual cycle is usually described from the point of the ovaries and is split into two phases – the follicular phase and the luteal phase. Sometimes people describe the uterine (womb) cycle which has three phases – menstruation (the period), the proliferative phase and the secretory phase.


The basics of the menstrual cycle

The cycle starts on day 1 which is the first day you wake up bleeding. You then keep counting the days until the first day of your next period when you start at 1 again. The “textbook” menstrual cycle is 28 days long but anything from 21-35 days is considered “normal”.


Let’s use a 28-day cycle as an example. The follicular phase is day 1-14 (assuming you ovulate on day 14) and then the luteal phase is day 15-28 (between ovulation and the beginning of your next period).


The follicular phase varies a lot in length between women, while the luteal phase is usually 14 days long. This means that you ovulated 14 days before your period starts. This can make it tricky to work out when you are ovulating because you don’t know for certain when your next period is going to start. This is even harder if your periods are irregular.


A woman with a 28-day cycle will usually ovulate around day 14 but this is not exact and even women with regular cycles will not necessarily ovulate on the same day of their cycle every month. Some women use cycle tracking apps or a diary to track their cycle and work out when they are ovulating. However, soon we will have an even better way of knowing this so keep an eye out for hormonas hormone test.

Ovulation is the key to pregnancy

It can be very stressful to try and work out when you are ovulating and then try to time having sex around this. This stress can then have negative effects on your body and can actually reduce the chance of you getting pregnant. If you want to have a baby just have sex regularly and try not to worry too much about the timing of it all.

If you want more information about the menstrual cycle, check out our article about irregular periods. It explains the basics of the menstrual cycle before it explains irregular periods (if you aren’t interested in the irregular periods part). 


How do I avoid getting pregnant?

The most effective way to avoid a pregnancy you don’t want is by using different types of contraception (birth control). There are lots of different options that you can use.

The average fertility rate of a woman in her 20s is about 85%. This means that if 100 women have unprotected sex (sex without contraception or birth control) for a year then 85 of them will get pregnant.

No contraceptive is 100% effective at preventing pregnancy. They all have a “failure rate” which might change depending on how “user-dependent” the method is (e.g. remembering to take your pill). Most contraceptive methods are more than 90% effective if used properly. This means that of the 100 women having sex for a year, only 10 will get pregnant (and this is actually less than 1 for methods like IUDs/implants etc).

Using natural fertility awareness can also be used as a way to prevent pregnancy.

What is assisted reproductive technology (ART) and how can it help with fertility?

ART is a word used to describe lots of different technologies that can help people to have a baby. Some of the techniques include in vitro fertilisation (IVF), intrauterine insemination (IUI), intracytoplasmic sperm injection (ISCI), egg or sperm donation and surrogacy. They have fancy, confusing names but essentially are all ways of getting around particular problems that might be making it hard for someone to have a baby. Infertility (being unable to get pregnant by having sex) is very common and can be caused by lots of different things. Approximately 1 in 7 couples have trouble getting pregnant these days and a lot of people choose to try ART.

One of the problems these days though is that some people think that ART will guarantee them a baby. Unfortunately, the technology isn’t that good yet. ART can help increase the chances of having a baby if you are struggling with infertility, but it doesn’t necessarily mean it will work. This can be really hard for people to come to terms with and can make the process very stressful.

Funding ART

The other thing is that, in the UK, the funding for fertility treatment depends on where you live. This is something many people are trying to change but, at the moment, depending on where you live, you might be able to access treatment through the NHS or you might not. If you can’t have funded treatment, ART is very expensive, which is something else to consider.


This YouTube video has some more information if you are interested.


Egg Freezing

Egg freezing is an option for women where we can freeze our eggs and “save them for later”. This is to try and slow down the ticking of our biological clock as the quality of our eggs decreases with age as well as the number we have. Egg freezing is becoming more common. Some tech companies are even offering egg freezing as a “perk” of working for their company. This is a pretty controversial issue at the moment, but I won’t get into the ethical discussion of it all.


The bottom line is that by freezing our eggs we may buy ourselves some more time to do things like find a partner, finish university, build our career, go travelling or do whatever it is we want to do before we have children. BUT (there was always going to be a but), this is still not a guarantee that you will be able to have a baby later. Egg freezing is often talked about as being an “insurance policy” to prolong the time we have to have children. Unfortunately, its success is still limited by the technology available for ART and, as I said before, this isn’t THAT good yet. It is also expensive!


So, freezing your eggs might be an option for you. BUT it is important to think of it as a “back up” plan rather than plan A. Especially if having children is something that is really important to you.


Men’s fertility

We shouldn’t forget about men when we talk about fertility because no matter who you are and how you want to have a baby, you will need sperm to do this.

Men are often thought of as being fertile throughout their adult lives. This is true and false at the same time. Men produce sperm from puberty throughout their life, however, the quality of the sperm declines with age. There are also many conditions that might affect a man’s fertility. If a couple is struggling to get pregnant then it is not necessarily the woman’s fault!


How Lifestyle Affects your fertility

Sometimes it is just bad luck and people struggle to get pregnant for no apparent reason.

There are some things that you can do to improve your chances though:

  • Stop smoking (both you and your partner)
  • Eat a healthy diet
  • Exercise
  • Try and keep your weight within the “healthy” range
    • This is a tricky one because the stress of trying to lose weight might actually just make everything worse
    • Making healthy choices about diet and exercise is the most important thing
    • There are limitations on fertility treatment funding based on BMI. If you are thinking about having fertility treatment they may require your weight to be in a certain range to be eligible for funding
    • Being underweight can also make it more difficult to get pregnant
  • Take folic acid while you are trying to get pregnant
    • Ideally women should take folic acid from 3 months prior to pregnancy
  • Prevent sexually transmitted infections (STIs) by using condoms
  • Get tested regularly for STIs throughout your life (even if you don’t want a baby any time soon)
    • STIs can cause damage to your fallopian tubes which can make it difficult to get pregnant in the future
    • The earlier an STI is diagnosed and treated the less likely it is to cause you problems in the future
  • Avoid alcohol if you are trying to get pregnant
    • Heavy drinking can also affect ovulation


Too long, didn’t read Take away:

  • Yes it is true that female fertility declines as we age
    • Statistically, it is harder to get pregnant in your 30s than your 20s, and even harder in your 40s
  • If you want to have a baby, have sex every few days. Try not to worry too much about getting the timing perfect
  • There are medical technologies that can help you have a baby if it is not happening naturally/you don’t have a partner/you’re in a same-sex relationship. BUT these are not a guarantee you will have a baby
  • Men can have trouble with fertility too
  • Lifestyle factors such as your weight, smoking/drinking habits can have an effect on your ability to get pregnant. You can try to modify them to improve your chances


References and resources:

Note: Just be aware that the rules about fertility treatment and the technologies available are different around the world. Some information might not be relevant to you depending on where you live.

NHS website on infertility

Your Fertile Years by Professor Joyce Harper

Professor Harper’s YouTube Channel

British Fertility Society


Reproductive Facts

Habbema, J.D.F., Eijkemans, M.J., Leridon, H. and te Velde, E.R., 2015. Realizing a desired family size: when should couples start?. Human Reproduction, 30(9), pp.2215-2221.


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Posted By  : Katherine Maslowski

Katherine Maslowski

Katherine Maslowski

Katherine is a junior doctor from New Zealand who has experience working in Obstetrics and Gynaecology and is currently studying an MSc in Women’s Health. She is passionate about women’s health and empowering women to learn about their bodies and understand how they work. She is particularly interested in sexual and reproductive health and helping women to make educated, informed choices about their health and wellbeing.