The popular myth that you can’t get pregnant when menstruating is as old as the hills. While it is true that you are unlikely to get pregnant while you have your period, it is not impossible to conceive at this stage of your monthly cycle.
It is true that you are at your most fertile during the three days leading up to ovulation and the 24 hours after ovulation.
One study of 782 healthy couples found that nearly all pregnancies occurred during this ‘fertile’ window. Sperm can survive in the fallopian tubes for several days, but an egg has to be fertilised within 24 hours of being released by the ovary, so having sex in the days leading up to ovulation means there are sperm available to fertilise the egg when it is released.
But, as Dr. Carole Gilling-Smith, Medical Director at the Agora Clinic, explains, your fertile window depends on your cycle length:
“For women with a 28-day cycle the fertile days are those leading up to day 14, the day of ovulation. But if you have a shorter cycle you ovulate earlier.
For example women with a 21-day cycle can ovulate as early as the seventh day after their period starts and for some this might mean they are still menstruating when they conceive.”
What’s more, if you have breakthrough bleeding or ‘spotting’ between periods, it can make it harder to establish when your period starts and ends, making it more difficult to work out exactly where you are in your menstrual cycle.