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Eight facts you may not know about fertility

Medical & health articles

For some women, the path to having children is straight and (relatively) stress-free. For many others, it's filled with roadblocks and complicated twists and turns. Also, some women may choose to bypass having kids altogether.

But whichever route you're travelling in life, it helps to understand the facts about fertility, so you can make informed decisions and plan as best you can for your journey ahead.

Here are eight facts that you may not know about fertility.

1. There are only six days in a woman's menstrual cycle when pregnancy is possible.

The six days when pregnancy is possible are what's known as a woman's 'fertile window'. Exactly when these days occur in a menstrual cycle depends on how long the cycle is – and this can vary a lot among women.

The six days of the fertile window include the day of ovulation (when an egg is released from an ovary) and the five days beforehand. Pregnancy is possible if you have sex (intercourse) on these days.

Your chance of becoming pregnant is greatest if you have sex during the two days leading up to ovulation, or on the day of ovulation

2. When it comes to age and fertility, it is the combination of both partners' ages that determines the likelihood of pregnancy.

Many of us know that a woman's age is the most important factor affecting her fertility, but a man's age also plays a part in the odds of achieving a healthy pregnancy.

Research shows that men younger than 40 have a better chance of fathering a child than those older than 40, and this is likely due to sperm quality decreasing with age.

A woman's fertility starts to slowly decline in her early 30s and speeds up at about the age of 35, with a decline in egg quality.

For couples trying to get pregnant when the woman is aged 35 or younger, their monthly chance of getting pregnant is about 20%, or one in five. By age 40, the chance of pregnancy is about 5% each month.

3. The male partner's weight can affect a couple's ability to have a baby.

For both men and women, being a healthy weight can increase the chance of pregnancy and having a healthy baby. Men who are overweight or obese have poorer sperm quality and are not as fertile as men of a healthy weight. For women, being overweight – or underweight – can impact hormone levels, the menstrual cycle and the quality of eggs.

Healthy eating, regular exercise and losing even just a few extra kilos can boost both male and female fertility.

4. A woman's caffeine intake may impact how long it takes to get pregnant.

The research is not entirely clear on this topic, but several studies have shown that women who consume large amounts of caffeine may take longer to become pregnant and may have a higher risk of miscarriage.

Caffeine can be found in varying amounts in coffee, black and green tea, energy drinks, chocolate and some soft drinks such as cola.

It is recommended that women limit their caffeine intake to 200mg per day (about two cups of coffee) if they are pregnant or trying to get pregnant.

5. STIs (sexually transmissible infections) can damage the reproductive organs and cause infertility.

If left untreated, STIs such as chlamydia and gonorrhoea can go on to cause reproductive complications such as pelvic inflammatory disease (PID), which can cause fallopian tube blockage that can lead to infertility.

These STIs can also affect male fertility if left untreated. They can harm sperm quality and cause damage to the male tubes.

What's more, chlamydia and gonorrhoea often have no symptoms – or the symptoms are mistaken for something else – and people may not even know they are infected and/or endangering others.

The good news is, these STIs are easily diagnosed and treated by your doctor, so it's important to have routine STI screenings and always practise safer sex.

6. IVF treatment cannot overcome age-related infertility.

Many people believe that IVF is a good back-up option for having children at a later age. However, this is not the case when it comes to couples using their own eggs and sperm. The technology of IVF cannot make up for the natural decrease in fertility that comes with age.

For couples having IVF, the chances of having a baby are higher if the woman is younger than 35 years of age and decreases significantly after 40 years of age. The chance of having a baby after one IVF cycle for women aged between 40 and 44 is only about 5%.

On the male side of the equation, the chance of having a baby with IVF is higher if the man is younger than 41 years of age.

7. Even if you have already had one baby, it does not mean you can easily have another.

If a woman has already had one or two children and wants a second or third child, her age at that time is the most important factor in determining the chance of that happening.

So, if a woman is 37 when she has her first child and then tries for a second child when she is 40, the monthly chance of getting pregnant is still the same as a 40 year-old who has not yet had a child – only 5%.

8. Sperm don't act alone in the journey towards reaching the egg.

While sperm need to be strong swimmers in order to reach the end-goal of the egg, they are by no means acting alone in their mission.

In fact, a good portion of a sperm's journey is helped along by the woman's muscles in her uterus (womb), which naturally tense and relax to gently coax the sperm along the fallopian tubes towards the egg. What teamwork!

Parting advice

It's important to remember that no matter how healthy or young you are, sometimes it can be difficult to get pregnant.

If you have been trying to get pregnant for 12 months or more – or six months if you're a woman older than 35 years – it's time to talk to your doctor about what to do next.

Read more about fertility and pregnancy or visit the Your Fertility website.

All rea­son­able steps have been tak­en to ensure the infor­ma­tion cre­at­ed by Jean Hailes Foun­da­tion, and pub­lished on this web­site is accu­rate as at the time of its creation. 

Last updated: 
18 January 2024
Last reviewed: 
23 July 2024