In the vagina, sperm survive only a few hours. The ones that reach the mucus of the cervix around ovulation can live there for up to five days, which is why sex several days before ovulation can lead to pregnancy.
In the vagina: a few hours at most
The vagina is naturally acidic. That protects you against infection, but it damages sperm quickly. Seminal fluid shields them for a short while, long enough for the most active ones to reach the cervix.
The rest of the semen leaks out, often when you stand up or the next morning. That’s normal and doesn’t lower your chances of pregnancy: we explain why in our article on semen leaking out after sex.
In the cervix, uterus and tubes: up to five days
For most of the cycle, cervical mucus is thick and acts as a barrier. In the days before ovulation it turns clear, slippery and stretchy, like raw egg white. It then lets sperm through, nourishes them and holds them in its folds.
From this reservoir they move up towards the uterus and Fallopian tubes over several days. In fertile mucus they usually survive two to three days, and up to five.
The egg lives about a day
After ovulation, the egg can be fertilized for only about 12 to 24 hours. Your fertile window is therefore about six days long: the five days before ovulation and the day itself.
Your chances are highest with sex in the two or three days before ovulation. The sperm are then already waiting when the egg is released.
What this means if you’re trying to conceive
There’s no need to aim for the exact day of ovulation, which is hard to predict. Sex every two to three days throughout the cycle is enough to make sure there are always sperm waiting.
What this means for contraception
Unprotected sex several days before ovulation can be enough to get pregnant. And because the timing of ovulation varies from one cycle to the next, no day is completely safe if your cycles are short or irregular, even during your period.
After unprotected sex, emergency contraception is an option. It works better the sooner you use it, so talk to a pharmacist, midwife or doctor without waiting.
And outside the body?
In the open air, sperm die quickly once semen dries. You can’t get pregnant from a sheet, a towel, a toilet seat or bath water.
Semen left at the entrance of the vagina, however, can still travel up. The fluid that comes out before ejaculation can also contain sperm, so withdrawal isn’t a reliable method of contraception.
Common myths
- Peeing or washing after sex prevents pregnancy. No. The sperm that matter are already in the cervix within minutes.
- Douching flushes out the semen. No, and it upsets the natural balance of the vagina.
- You need to lie down to keep the semen in. You don’t.
- Semen leaking out means it didn’t work. No, it says nothing about your chances.
- Discharge the next day is always semen. Not necessarily: it’s often cervical mucus or your usual discharge. See our article on discharge after sex.
When to see a doctor
- After unprotected sex, if you don’t want to be pregnant: as soon as possible, for emergency contraception.
- A late period after unprotected sex: take a pregnancy test.
- No pregnancy after 12 months of regular sex without contraception, or after 6 months if you’re 35 or older.
- Very irregular or absent periods, which can point to a problem with ovulation.
