Only when you ovulate is there an unfertilised egg waiting for a sperm cell. Once an egg comes into contact with sperm, it becomes fertilised and attaches itself to the womb. This starts the conception process and you become pregnant.
If you have sex before you ovulate, sperm can hang around for days in your fallopian tube waiting for an egg to pop out. If you have sex after you ovulate, the egg will be ready and waiting for the sperm to arrive.
But remember, having sex only at other times of the month is not a reliable way to avoid getting pregnant!
Fertile and most fertile
What’s the difference between being ‘fertile’ and being ‘most fertile’? If you’re fertile, it means you’re able to get pregnant – you’ve reached puberty and your ovaries are working properly. You’re most fertile around the time of ovulation, so you’re most likely to get pregnant if you have sex at this time.
You can get pregnant from the first time you ovulate, so even before you have your first period. On the other hand, just because you’ve started your periods doesn’t mean you can get pregnant.
In the first year you have your periods, an egg might only be released one in five times. By the time you’ve been having periods for six years, an egg will be released nine out of ten times.
But remember, if you don’t want to get pregnant, don’t play ovulation roulette – use contraception.
As you get older, especially over the age of about 30, you tend to become less fertile, and eventually you stop ovulating and having periods. On average, women are able to get pregnant between the ages of 15 and 49.
Fertility and weight
If you’re too big or too thin it can affect your chances of getting pregnant.
To get a rough idea of whether your weight could be affecting your fertility, you can work out your BMI.
BMI the complicated way
Your BMI is your weight (in kilos) divided by your height (in meters) squared. So if you weigh 72 kilograms and your height is 1.72 metres, your BMI is 72 divided by 1.72 x 1.72 = 24.9.
BMI the easy way
All that arithmetic sounds too much like hard work? Don’t worry, just go to an online BMI calculator like this one and it will do the maths for you!
Your BMI is considered to be ‘normal’ if it’s between 18.5 and 25 – though this is only a rough guide.
If your BMI is lower than about 18.5 or higher than about 28, you could be less fertile. So it’s important to eat as healthy and varied a diet as you can, and try to get your weight closer to the ‘normal’ range.