WHAT IS THE MENSTRUAL CYCLE?
The menstrual cycle is a monthly cycle in which a woman’s uterus prepares for a fertilised egg to settle. The uterus is also called the womb and is the part of a woman’s body in which babies grow. Most women start experiencing their menstrual cycle between the ages of 10 and 15 until they are in their 40s or 50s. The menstrual cycle has four phases and lasts around 28 days.
THE MENSTRUAL PHASE
The first phase is called the menstrual phase and is usually called the period. The period is the part of the cycle during which women experience blood flow out of their vagina. It usually lasts about three to seven days. Day 1 of the menstrual cycle is therefore the first day of bleeding a woman experiences during one of her cycles.
THE FOLLICULAR PHASE
The second phase is called the follicular phase and is the part of the cycle during which the female body prepares for pregnancy. The follicular phase includes the menstrual phase, so for a 28 day cycle, it would last from day 1 to day 13. Women have eggs inside their bodies which can grow into babies if they are fertilised by sperm. During each cycle, one egg becomes ready to be fertilised.
THE OVULATION PHASE
The third phase is the ovulation phase. This stage of the cycle is only around one day long and happens around halfway through the cycle, so for a 28-day cycle, it would happen on day 14 (14 days after the first blood flow). During this stage, the egg has finished being prepared and is ready to be fertilised. Women are most likely to become pregnant if they have sex before or during the ovulation phase. Sperm can survive inside the female body for up to a week, so if a woman has sex a few days before the egg is ready to be fertilised, the sperm can ‘wait’ inside her body for this to happen.
Because the length of a menstrual cycle varies between women, the time when they are most likely to become pregnant also varies between them. If on average you have a period every 28 days, you ovulate around day 14 and you have the highest chance of becoming pregnant if you have sex between days 11 and 14. If you have a short cycle of around 24 days between two periods, ovulation happens around day 10 and you are most likely to become pregnant if you have sex between days 7 and 10. If you have a longer cycle of around 35 days, ovulation happens around day 21 and you are most fertile between days 18 and 21. It is important to remember that these are just probabilities. You are not guaranteed to become pregnant if you have sex during these periods and you may also become pregnant if you have sex outside these periods, it is just less likely.
THE LUTEAL PHASE
The final stage is called the luteal phase. It lasts from day 15 to day 28. What happens during this stage depends on whether the egg was fertilised by a sperm. If it was fertilised, the egg moves into the uterus and eventually turns into a baby. If it was not fertilised, the lining of the uterus is shed through the vaginal opening, the period starts, and a new menstrual cycle begins.