How does ovulation work?
Ovulation is one of the most important parts of the menstrual cycle and female reproductive system. Understanding how it works helps you oversee your health and feel more confident in your body's ability when you are trying to conceive. Here you can learn more about how ovulation works, when it occurs, and what characterizes the four phases of a woman’s cycle.
What is ovulation?
The term ovulation means that a mature egg (in rare cases, more than one) has been released from your ovaries. After release, the egg moves down to the fallopian tubes, where is stays for 24 – 36 hours. During this period, it is possible for the sperm cells to fertilize the egg. Sperm cells can live inside the female reproductive system for up to five days, which means that if you want to get pregnant, you should have intercourse in the days before or on the day of ovulation.
When is ovulation?
Ovulation occurs approximately two weeks into your menstrual cycle and only happens once during every cycle. The ovulatory phase lasts about 5 days, in which the ovulation occurs. A menstrual cycle lasts about 28 – 32 days, the specific number of days varies from one woman to another. If you want to become pregnant, we recommend you start tracking your menstrual cycle and thereby learning more about your time of ovulation. You can track your ovulation by keeping a menstrual calendar.
What happens during ovulation?
Ovulation is an important part of the menstrual cycle, and to understand how ovulation works you also need to understand how the menstrual cycle functions. The menstrual cycle can be divided into four phases, which is illustrated on the graphic below. It starts on the first day of your period and ends the day before your next period starts. The length of each phase differs from woman to woman and depends on the total length of the cycle.
Illustration of the menstrual cycle
The menstrual phase: The cycle starts on the first day of your period, which is the result of the previous cycle where the mature egg was not fertilised. This phase normally lasts around 4-7 days.
The follicular or pre-ovulatory phase: This phase also begins on the first day of your period and normally lasts around 10-17 days. During these days, the level of your Follicle Stimulating Hormone (FSH) increases, which triggers your follicles to develop into mature eggs. Usually, between 10 and 20 follicles are released during every cycle, but only one follicle will develop into a mature egg and be released. Before the egg is released, the uterine lining thickens to prepare for implanting the mature egg into the uterus.
The ovulatory phase: Ovulation occurs in the middle of the menstrual cycle in response to a peak in the level of oestrogen, right when the follicular phase is over. The oestrogen level triggers a release of the Luteinizing Hormone, also called the lh surge. This hormone helps the egg to push through the ovary wall and into the fallopian tube within 24 – 36 hours where it is available for fertilisation. This is the optimal time for artificial insemination. If the egg is fertilised, it will stick to the uterine wall after a few days of transportation.
The luteal phase: The luteal phase lasts approximately 14 days and is the last stage in the cycle until the next menstrual phase begins unless fertilisation occurs. It marks a decrease in the level of FSH and LH. If the egg has not been fertilised, the body will shed the thickened uterine lining, and the menstrual cycle will start over.
In fertility treatment, the fertility doctor needs to time the insemination with your ovulation, which means that the treatment will be synchronized with your menstrual cycle, or you will receive a trigger shot containing Luteinizing Hormone, which will kickstart your ovulation. It does not depend on whether you are using sperm from a donor or your partner. If you want to read more about different types of fertility treatments like ICI, IUI, IVF, or ICSI then follow the links.
Ovulation facts
- Women are born with approximately 1 million follicles (pre-eggs)
- Every month, between 10 and 20 follicles are released from the ovary but usually, only one follicle will develop into a mature egg
- A mature egg lives between 12-24 hours after leaving the ovary
- The menstrual cycle normally lasts between 28-32 days, but some women may have shorter or longer cycles
- Ovulation might occur even if your period has not occurred and vice versa
- Ovulation may occur on a different day each month and at different times during your cycle