What is Ovulation?

Compared to menstruation, ovulation probably isn’t something you spent as much time in health class focusing on. Ovulation is the time of the month when an ovary releases the egg that has the potential to be fertilized. So what does it have to do with your menstrual cycle? Let’s run through the basics of ovulation and what it means for you.

What is ovulation?

ovaries uterus womb

The ovaries are two organs on either side of the uterus, both about the size of an olive. The ovaries contain your lifetime supply of follicles – these are the tiny dormant sacs that contain egg cells. Once per menstrual cycle, an ovary gets a hormonal signal from the brain saying it’s time to prepare an egg for fertilization.

This causes about 20 of the dormant follicles to “wake up” and start maturing. Most will die away naturally, but one of these follicles – the dominant follicle – will continue to grow until it reaches about 0.8 inch across. When it’s large enough, the egg cell (oocyte) bursts forth from the follicle, where it is swept up into the outskirts of the fallopian tubes that connect to the uterus. This process is called ovulation.

How long does ovulation take?

menstrual cycle hormone level luteal phase period follicular phase

The graph above is an example of a woman’s Basal Body Temperature (BBT) over the course of one menstrual cycle. BBT refers to the body’s temperature before without any additional activity, such as first in the morning before getting out of bed. Before and after ovulation, there is a change in of about 0.5 to 1.6℃. Therefore, the period of lower temperatures and higher temperatures on the graph above correspond to the phases before, during and after ovulation.

Follicular phase

Lasting about 14 days on average (though it can be up to 25 days in some cases), this is the time of the cycle when the ovarian follicle is growing and developing.


The mature follicle rupture and releases an egg cell. If it’s not fertilized in the next 24 hours, then it will die and no pregnancy will occur.

Luteal phase

During the luteal phase, the leftover bits of follicle turn into a structure called the corpus luteum. This releases hormones that get the endometrium lining of the uterus ready to support a pregnancy. If no pregnancy occurs, then this lining is shed out in the next menstrual period.

Ovulation and Basal Body Temperature

clinical thermometer

By measuring your Basal Body Temperature first thing in the morning over your cycle, you’ll be able to identify when ovulation occurs. This is a good habit to get into if you’re trying to conceive, as your most fertile days are 2 to 3 days before and 12 to 24 hours after ovulation.

However, keeping track of a BBT graph like this can also give you other insights. For example, if your graph doesn’t form a neat two-phase pattern, it could point to issues such as a hormone imbalance, endometriosis, or an anovulatory cycle (where an egg isn’t released).

Ovulation is the first step towards pregnancy

smile beach sea happy relax

If the ovulation process is news to you, you’re not alone — but hopefully this gives you a better idea of your other time of the month. If you have sex during the fertile window before and after ovulation, you’re more likely to get pregnant. That means that tracking your ovulation date by Basal Body Temperature can be an empowering step to take if you’re trying to conceive.