The menstrual cycle
A woman’s menstrual cycle has three phases, with the first day of your period signalling the start of the cycle:
- The follicular phase, which lasts for about 14 days. During this fortnight, follicles in the ovary will reach maturity, and a single one of them will develop into a mature egg (an ovum). Your period begins right at the start of the follicular phase.
- Ovulation, which takes place over 24 hours. When FSH (follicle stimulating hormone) reaches peak maturity, another hormone, LH (luteinising hormone), is secreted and causes the egg to be released from the follicle. The egg is then carried along into the Fallopian tubes. If it’s not fertilised, it’s shed, and you get your period.
- The luteal phase, which lasts for 14 days. During this time, the egg secretes corpus luteum, luteal hormone and progesterone. Progesterone prepares the womb lining for an egg to be implanted.
These different phases overlap, which is why the overall length of the cycle can seem longer than 28 days!
To calculate your ovulation date, you should bear in mind that no matter how long your entire cycle is, the luteal phase always lasts for 14 to 15 days.
To find out your ovulation date, you need to remove these 14 days from the whole of your average cycle. For example, if your cycle is usually 24 days long, ovulation will take place on the tenth day (24 – 14 = 10).
The fertile window
To have the best chances of conceiving, you need to allow a few days before and after the calculated ovulation date: the egg has a lifespan of 24 hours and the sperm cells up to 4 days, which gives a window of about 6 days.
How to recognise ovulation
- Body temperature increases (take your temperature in the morning as soon as you wake up, before getting out of bed) by 3 to 5 tenths of a degree.
- Cervical mucus becomes clearer, with more abundant fluid.
- You might experience some pain in your lower stomach, on the side where the ovary has released the ovum.
There are tests available in pharmacies, in the form of little strips that, upon contact with urine, enable you to identify whether you’re ovulating (by detecting the presence of the LH hormone). If you’re trying for a baby, this detector is 90% accurate at letting you know whether you’re in a fertile period.