How Can I Tell When I'm Ovulating?

Aparna Ramanathan, MD MPH FACOG
Aparna Ramanathan, MD MPH FACOG
Published: April 4, 2022Updated: April 5, 2022

Reviewed by Dr. Lisa Czanko MD, MPH

You’re getting ready to take the big leap and start a family. This can be an exciting time, but waiting for that positive pregnancy test result can be stressful as well! Between work, family, and all the other demands of life, you may be wondering if there are ways you can optimize your chances of getting pregnant. The good news is that there are!

First, some basics

First, let’s cover some basics about how periods and fertility are related. The time between the start of one period to the start of the next is one menstrual cycle. This cycle is normally between 21 to 35 days and can be divided into two halves. The first half is called the follicular phase and the second half is called the luteal phase. 

The luteal (second) phase is consistently 14 days long. Ovulation, which is when an egg is released from the ovaries, occurs on day one of the luteal phase. Once the egg is released, it can be fertilized by sperm and create a pregnancy. 

The length of the follicular (first) phase varies depending on how long the overall menstrual cycle is. For example, if a cycle is 28 days long, then the follicular phase is 14 days long (28 days minus 14 days for the luteal phase). But if a cycle is 21 days long, then the follicular phase is closer to seven days long (21 days minus 14 days for the luteal phase). So, to figure out when ovulation is generally occurring, take the predicted first day of the next period and subtract two weeks (14 days). 

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Menstrual Cycle Tracking

People whose menstrual cycle lengths do not vary more than a few days from month to month can use cycle tracking to help figure out when they might be most fertile. The fertile window in the menstrual cycle can last approximately six days, including the day of ovulation and the five days before. So, if someone tracks their period on a calendar for a few months, they can predict when their next period will start and subtract two weeks to find their most likely ovulation day. Subtracting five more days before that will identify the most likely start of their fertile window. 

Generally, it’s recommended that people to have sex every other day during the fertile window if trying to get pregnant. It may come as a surprise, but having sex every day during the fertile window does not increase the odds of getting pregnant and, for some, it can make sex seem like a chore instead of a fun and intimate way to spend time together.

Basal body temperature monitoring 

People can use changes in their body temperature to figure out when they are ovulating as well. The hormones released during ovulation can raise body temperature by about 0.5 degrees Fahrenheit. Detecting changes in body temperature is easy, non-invasive, and can be done at home. All a person needs is a basal body thermometer which they can get at any pharmacy. It is recommended that people check their temperature every morning before getting out of bed, using the bathroom, or eating and drinking anything. Although temperature may vary slightly from day to day, a consistent 0.5 degree increase can be seen with ovulation and in the ten days following. Because the change in temperature only happens with ovulation, basal body temperature monitoring is not as useful in helping people time sex, but can be useful for a person trying to get a sense of what their ovulatory pattern is over several months.

Ovulation Kits

The surge of the luteinizing hormone (LH) that happens just before ovulation can be detected with at-home urine tests sold in over-the-counter ovulation kits. The surge typically happens around 36 hours before ovulation, so a positive test can be used by people to help time sex. 

Cervical Mucus Assessment

People can evaluate their cervical mucus secretions to determine which days they are potentially fertile. On fertile days, cervical mucus tends to be wet, slippery, transparent, or stretchy.  People can time intercourse based on changes in cervical mucus to improve their chances of pregnancy. This method requires checking cervical mucus secretions multiple times per day for best results. Some people keep a chart that describes whether or not they have secretions and the character of the secretions to get a sense of when their fertile days fall during the menstrual cycle. A cycle tracking app can also be useful here as people can easily make note of what their cervical mucus was like that day. 

Generally, it’s recommended that people to have sex every other day during the fertile window if trying to get pregnant.

Beyond the Basics

For people experiencing difficulty getting pregnant despite having regular unprotected sex for six months, a consultation with a medical provider can be helpful to determine if any further tests are needed. 

Our Simple Note: 

We know that the idea of cycle-tracking can feel like a lot of work and may lead to frustrations. If possible, try to remain open-minded and engage with positive thoughts surrounding your fertility journey. If you find that you are getting frustrated with all the numbers, tracking, and logging, take a break for a bit, recharge and talk about it with someone you care about. Remember you can always reach out to a medical provider for more help.

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2. Taylor AE, Khoury RH, Crowley WF Jr. A comparison of 13 different immunometric assay kits for gonadotropins: implications for clinical investigation. J Clin Endocrinol Metab. 1994;79(1):240. 

3. Sherman BM, West JH, Korenman SG. The menopausal transition: analysis of LH, FSH, estradiol, and progesterone concentrations during menstrual cycles of older women. J Clin Endocrinol Metab. 1976;42(4):629. 

4. Adams JM, Taylor AE, Schoenfeld DA, Crowley WF Jr, Hall JE. The midcycle gonadotropin surge in normal women occurs in the face of an unchanging gonadotropin-releasing hormone pulse frequency. J Clin Endocrinol Metab. 1994;79(3):858. 

5. Sinai I, Jennings V, Arévalo M. The TwoDay Algorithm: a new algorithm to identify the fertile time of the menstrual cycle. Contraception. 1999;60(2):65. 

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