So just what are the chances of getting pregnant? Here’s what other sex educators might not tell you about fertility.
Ok, I’m going to let you into a little secret. Just don’t tell any other sex educators I told you this. If you have penis in vagina sex without a condom or contraception, you won’t always get pregnant. In fact, it’s unlikely because chances of pregnancy are quite low. BUT WAIT!
Don’t run off to have bareback sex! This doesn’t mean it won’t happen. Some people have unprotected sex once or twice and they get pregnant straight away. However I’m just being honest with you.
Even though you should use contraception for penis in vagina sex, the chances of getting pregnant are lower than you might think. I’ll explain here, but first here’s a recap of how fertilisation works.
How fertilisation works
An egg is released from the ovary once in a menstrual cycle. If it meets with sperm while it is travelling down the fallopian tube then fertilisation and then pregnancy can start.
If a sperm meets an egg at this stage then there is a 33% chance of fertilisation. Fertilised eggs then need to stick to the lining of the womb in order for a pregnancy to start. The egg dies around 20 hours after being released. After that it is not possible to get pregnant until the next egg is released in the next cycle.
So, as you can see, it’s harder than you might think to get pregnant, but you definitely should use contraception if you don’t want to get pregnant (keep reading). Also there’s is a ‘time of the month’ when you can’t get pregnant. How to work that out though? Well it’s very very difficult because it’s all about the menstrual cycle.
How the menstrual cycle works
Day one of a menstrual cycle is the first day of a period. Periods last for a few days and this varies. Eggs are released from the ovary (ovulation) roughly around half way through the cycle. In the example above a cycle that was 28 days long might have ovulation around day 14 / 15. In order for pregnancy to start, an egg has to be fertilised within a 20 hour time slot when the egg is alive. As sperm can live inside someone for 5 – 7 days then the time to avoid sperm getting into the vagina is from day 9 to 15. Once the egg has died it’s not possible to get pregnant until another egg is released which happens after the next period.
So if you knew when ovulation was definitely going to happen then you could decide for yourself if it ‘safe’ to have sex or not. However, it’s really really hard to do that.
Why you need contraception
If your cycles are *always* the same, you might be able to predict when you are going to be fertile and not fertile. But periods, and ovulation, are random. Because periods don’t always come when expected, the same is true for ovulation. Also ovulation is not always at the same time even if your menstrual cycle is the same. This means that people may be having unsafe sex when they think they are safe from pregnancy. If only our bums change colour when we ovulate – like baboons.
Some people are able to use this as a method of having sex and without having babies: however it’s very very hard to do and not super effective – click here for more. But but but, it’s not as effective as using condoms or other methods of contraception. For more advice and a clinic near you go here
‘I think I’m infertile’
Some people may have had sex a few times, not got pregnant and assumed that they were unable to have kids. Then they might think ‘I can’t get pregnant, so I won’t bother with contraception.’ They would be wrong. Remember, although pregnancy *can* happen the first time you have sex it would be unlikely. However if you have sex regularly over the course of a year then it is much more likely.
Are you panicking about pregnancy?
Here’s a paper which shows how people think they are infertile when they aren’t (and that this might make them decide not to use contraception).
The authors of this paper reckons that there is a 3.1% chance of pregnancy from a single, random act of sexual intercourse (which can increase to up to 9% leading up to ovulation and decreases to 1% at other times in the cycle).
Hope that’s cleared that up ….
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© Justin Hancock, 2023
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Justin Hancock has been a trained sex and relationships educator since 1999. In that time he’s taught and given advice about sex and relationships with thousands of young people in person and millions online. He’s a member of the World Association for Sexual Health.