Conception is the moment when egg and sperm meet. It can take anything from 45 minutes to 12 hours for a sperm to reach your fallopian tubes, which is where conception usually happens. However, sperm can survive inside your body for up to seven days, so conception can happen at any point in the week after sex, if you’re ovulating.
Inside the woman’s body: how an egg is hatched
For women, the possibility of pregnancy begins in the ovaries. These are the two small, oval organs attached to either side of your uterus (womb). The ovaries are packed with eggs, which are made before you are even born. Every baby girl is born with 1 to 2 million eggs in her ovaries. Many eggs begin dying off almost immediately and the rest steadily decrease in number as you get older. You’ll probably release about 400 eggs during your fertile years, between your first period and the menopause. In countries such as the UK, the average age of menopause is about 52.
During each menstrual cycle, sometime after your period, one to three eggs start to reach maturity in one of your ovaries. The ripest egg is then released, a process known as ovulation. The egg is quickly sucked up by the tulip-shaped opening of the nearest fallopian tube. There are two fallopian tubes, each about 10cm in length, which lead from the ovaries to the uterus.
Ovulation is usually about 12 to 14 days before your next period. The exact time of ovulation depends on the length of your cycle. Several different hormones work together to control the length of your cycle, when your eggs ripen and the timing of ovulation. You can read more about these hormones in our article on the menstrual cycle.
The average egg lives for up to 24 hours after release. It needs to be fertilised within this time by a sperm for a baby to be conceived. If your egg meets up with a healthy sperm on its way to the uterus, the process of creating a new life begins. If not, the egg ends its journey at the uterus and disintegrates.
If you have not conceived, the ovary stops making oestrogen and progesterone. These are the two hormones that would help maintain a pregnancy. When the levels of these hormones drop, the thickened lining of your uterus is shed during your period. The remains of the unfertilised egg are shed at the same time.
What happens while you’re having sex
In addition to all the fun, your bodies are building up tension that you hope will end in orgasm. Having an orgasm also has an important biological function. In men, orgasm propels sperm-rich semen into the vagina and up towards the cervix at roughly 10 miles per hour. The force of ejaculation gives the sperm a good head start on their way to the egg. A woman doesn’t need to orgasm for conception to happen. Gentle uterine contractions can help the sperm along, but these happen without you having an orgasm.
Many couples wonder if a particular sex position is best for conceiving. No one knows for sure. The most important thing about sex is that you’re both having a good time and you’re doing it often enough. For you to conceive, live sperm needs to be in your reproductive tract during ovulation.
Not all women ovulate during the middle of their cycle or at the same time in their cycle every month. To improve your chances of conception, aim to have sex every other day or so throughout your cycle.