What is Ovulation? When does Ovulation Occur?
If you are trying to conceive or preventing pregnancy, you may wonder “when do I ovulate?” or “when is my fertile window?”. These are often your most fertile time during a cycle, and days you will not want to miss if you are seriously trying for a baby. Get ready to learn more about your body and how this important phase of a menstrual cycle comes into play whether you are planning for a baby or preventing pregnancy.
What is ovulation?
Ovulation is a monthly reoccurring event when a mature egg is released from the ovary. It happens approximately once per month, toward the middle of a monthly cycle.
During ovulation, the egg travels down the fallopian tube, making its way towards the uterus. If it is fertilized by sperm along the way, it implants into the thickened uterus lining. The uterus lining and blood will shed if no conception occurs. The shedding together with the unfertilized egg will exit the body and this is your menstruation.
You may think you have an equal chance of pregnancy at any time during a cycle, but this is not true. You are most fertile on a few days before you ovulate and the day of ovulation.
When does ovulation occur?
You may have read online that you ovulate on day 14 every month, which is two weeks before the onset of the next period. This is more of a myth than truth. It is based on the average cycle length of 28 days, assuming there is no variation from cycle to cycle. The reality is every woman and every cycle is hugely different. So, you will want to track your ovulation to know when ovulation happens to you.
However, understanding your menstrual cycle is a great first step to learn your cycle and body. Your menstruation starts on day 1 of the cycle and ends right before the next period starts. Your cycle is divided into two phases, the follicular phase, and the luteal phase.
Follicle stimulation hormone (FSH), Estrogen and Luteinizing Hormone (LH) rise during the follicular phase, which starts on the first day of your period. They trigger the development of mature eggs and the release of an egg.
The luteal phase o fa menstrual cycle starts right after ovulation. If the egg is fertilized, it implants into the uterus lining, and the woman is considered as pregnant. If fertilization didn’t happen, the uterus lining and blood will shed, the period begins, and the next menstrual cycle onsets.
How does ovulation work?
Women are born with all the eggs they have. This means the number of eggs decreases as they get older.
At birth, there are about 1 million eggs each woman has. By the first period, the egg number has already reduced to 300,000 – 500,000. Of all these eggs, only 300-500 will ever reach full maturity to the point where they can be fertilized by sperm.
Follicles undergo a series of changes leading to ovulation. At the beginning of a menstrual cycle, there are about 10 follicles as candidates of ovulation of this cycle. Gradually, one will become dominant during the follicular phase. This is just like the best athlete being selected from the pack. All resources then go to this egg and the others die out.
All these changes are tightly controlled by your hormones. The first is FSH or the follicle-stimulating hormone, and another one is LH or the luteinizing hormone. The FSH increases slightly, stimulating the development of several eggs containing follicles. Only one of these follicles develops into a mature egg, producing Estrogen hormone, which often rises about 5 days before ovulation.
The LH hormone surges about 12-24 hours before ovulation, triggering the release of the egg into the fallopian tube. After the egg is released, it has only up to 24 hours of life span to be fertilized by the sperm. Fortunately, sperm can live in the woman’s “fertile mucus” – which usually feels like egg whites – up to 5 days, your fertile days are the 5 days leading to ovulation plus the ovulation day. See how Mira works to track your hormone curve just like how it is done in the lab.
How to track ovulation?
Being able to identify your timing of ovulation is key to a successful conception. Here are a few of recommendations and signs of ovulation popularly practiced by women:
1. Track your actual hormone level by Mira. By seeing your actual hormone curve, you are able to identify your fertility peak regardless of the cycle variation. Mira uses AI to learn and analyze your cycle, so you can get doubled accuracy of cycle prediction after using Mira for 4 months.
2. Ovulation prediction kits (OPK) also tests the LH hormone. However, the “smiley face” vs. “no smiley face”, or the “two lines” vs. “one line” doesn’t adapt to your cycle variation. It is very common that the difference from cycle to cycle, and woman to woman, is huge. Although they are easy to use, you will likely get into false-negative and miss the few most fertile days of a cycle.
3. Basal body temperature rises about 0.5 Ferhenight 12 hours after ovulation. It is too late to try to conceive then because egg only lives up to 24 hours after you ovulate. Basal body temperature doesn’t show a sign for the 5 fertile days leading to ovulation. It can be used to confirm ovulation, but not a good sign to predict ovulation.
4. Our fertile cervical mucus often looks like egg white during the fertile days. It is a nice way to learn more about your body, but it usually takes more than 6 months to learn how to look at it. It is also affected by sex, infection, and exercise.
✔️ Medically Reviewed by Banafsheh Kashani, MD, FACOG
Banafsheh Kashani, M.D., FACOG is a board-certified OB/GYN and specialist in reproductive endocrinology and infertility at Eden Fertility Centers, and has been treatingcouples and individuals with infertility since 2014.
Dr. Kashani has conducted extensive research in female reproduction, with a specific focus on the endometrium and implantation.
Additionally, Dr. Kashani has authored papers in the areas of fertility preservation, and fertility in women with PCOS and Turners syndrome. She also was part of a large SART-CORS study evaluating the trend in frozen embryo transfers and success rates.