The Fertile Period: The Best Time to Conceive
The time in a woman's menstrual cycle when the chance of becoming pregnant is highest is called the fertile period. For a woman whose periods come regularly every 28 days, the fertile period is the six days from day 11 to day 16, counting from the first day of her last period. However, a pregnancy can happen outside this window too.
The menstrual cycle begins with the period. From then on, an egg starts to mature in the ovaries, ready to be released during that cycle. It usually takes about 14 days for an egg to mature enough to be released, although this can vary. The next period then starts exactly 14 days after the egg is released. Because this second part of the cycle does not change, the length of the cycle differs from woman to woman according to how long her egg takes to mature and be released.
Sperm can survive for about 5 days inside a woman's reproductive tract, and an egg survives for about two days after it is released. So for an egg and a sperm to meet and fertilisation to happen, it is enough to have intercourse on a day close to ovulation (the release of the egg). Research has shown, however, that the chance of pregnancy is highest from 3 days before ovulation (usually day 14 of the cycle) to 2 days after it. That is why the time from three days before ovulation to two days after it is regarded as the fertile period.
If your periods are irregular, the reason is that the time your egg takes to mature varies, or that no egg matures at all. Ovulation is then hard to predict, so the fertile period cannot be calculated. If your periods come regularly after the same number of days, ovulation happens 14 days before your next period is due. Because the time an egg takes to mature and be released can vary, the length of the menstrual cycle differs from one woman to another.
You can work out your fertile period by entering the length of your cycle and the first day of your last period in our calculator.