How does pregnancy happen?
When a single sperm fuses with an egg it is called fertilisation. Pregnancy starts several days after fertilisation.
Pregnancy does not begin until the fertilised egg has implanted in the womb, after having travelled through the fallopian tube.
So, if you’ve just had unprotected sex or contraceptive failure, no pregnancy will start until at least the sixth day. This means you have time to take the morning after pill if pregnancy is not right for you at the moment.
Signs of pregnancy
If you think you might be pregnant, take a pregnancy test and/or visit your doctor. If you are pregnant it is too late for emergency contraception because it works to prevent an unintended pregnancy. It will not affect an existing pregnancy.
When can I get pregnant?
In theory, during the average woman’s menstrual cycle there are six days when sex can result in pregnancy. This conception risk period, also called the ‘fertile window’ is the five days before egg release (ovulation), plus the day of egg release.
Are you at risk?
You are at risk of conception if you have unprotected sex in the five days before ovulation because sperm can live for about five days, and can be waiting in the fallopian tubes, ready to fertilise your egg. Unless fertilised, an egg only lives for 24 hours.
The highest risk of pregnancy is when ovulation happens shortly after unprotected sex.
Sperm viability declines in the days after sex. This means the risk of conception is highest when ovulation happens during the first three days following unprotected sex.
When am I most fertile?
You have no way of knowing when your fertile window is – and it can be at a different time every month.
This means you are at risk of pregnancy almost throughout the whole of your menstrual cycle.
- You might not ovulate on the same day of your cycle from one month to the other
- Women with a regular cycle can be in their fertile window any time from day 6 to day 21
- Women with an irregular cycle can be in their fertile window from day 8-28
What happens when a woman ovulates?
Ovulation is the release of an egg from the ovaries. A woman is born with all her eggs. Once you start your periods, one egg (occasionally two) develops and is released during each menstrual cycle.
After ovulation, the egg lives for approximately 24 hours
Once the egg is released from the ovary it travels down the fallopian tube towards the womb. Fertilisation happens if sperm meets and fuses with the egg. Sperm can survive in the fallopian tubes for up to five days after sex.
If the egg is not fertilised, hormone levels fall, and the womb lining comes away and leaves the body as a period.
A woman cannot get pregnant if ovulation does not occur.
Your menstrual cycle
The menstrual cycle is the process where an egg develops each month and the lining of your womb is prepared for possible pregnancy.
The menstrual cycle is driven by body chemicals called hormones. A cycle is counted from the first day of bleeding (your period) to the first day of your next period. The rise and fall of hormonal levels during this time control the menstrual cycle.
What’s happening in your womb
What’s happening to your hormones?
The menstrual cycle is controlled by a complex interaction of hormones. In each cycle, increasing levels of hormones cause the ovary to develop an egg and release it (ovulation). The womb lining also starts to thicken.
The female reproductive system
The reproductive system, sometimes called the sexual organs, is the set of organs needed to make a baby, or reproduce.
The female reproductive system is made up of a vulva, vagina, cervix, womb, fallopian tubes, ovaries and breasts. Unlike men, most of your reproductive system is located inside the body.