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Detecting Ovulation: How to Get Accurate Results

Detecting Ovulation: How to Get Accurate Results

Ladies! Knowing your fertile window and when you ovulate is necessary in order to have a chance at natural conception each cycle. We know detecting ovulation on your journey to try to conceive is critical. Yet, there are so many methods available, and they don’t all work the same or provide accurate results. Today, many women we talk to are unsure of when they’re in their fertile window or ovulating, and what method of ovulation detection really works the best. Your fertile window is truly unique to you!

Demystifying the Fertile Window

Timing intercourse during your fertile window, of course, offers your best opportunity for conception. But, what is the fertile window? Most experts consider the fertile window to last at least 5 days. From our experience, it includes the 3 days before ovulation, the day of ovulation and, for some, the day after ovulation. According to research published in the New England Journal of Medicine, most women actually become pregnant the day of ovulation or in the two days that precede it.

Sounds easy? It should take only some simple math to detect ovulation, right? We hope so, yet there are a few sticking points to watch for when tracking ovulation.

1. Ovulation timing can shift. You may not ovulate on the same day each month. If you’re Fertility Charting with BBT (tracking basal body temperature), you already know this. One month, you may ovulate on day 10; other months you may ovulate on day 14; and so on. If you’re under a lot of stress, have fertility challenges, are in perimenopause, or even if you travel, you may skip ovulation altogether or have an irregular ovulation pattern.

New research from the National Institute of Environmental Health Sciences, shows that only about 30% of women experience their fertile window between days 10 and 17 of their menstrual cycle. Ovulation and the fertile window may be especially hard to predict in the teenage years and during pre-menopause when the cycle is more likely to be irregular.

2. Your BBT fertility chart (while still a favorite technique) confirms ovulation after it happens. So, you have to chart for a cycle or two (or perhaps more) to get the hang of seeing your ovulatory patterns. Here’s a helpful clue for BBT charters when you first get started: Many women see a slight temperature dip (about ½ a degree) the day of ovulation.

3. Consider more than one ovulation tracking method. Each method for tracking ovulation has pros and cons. I like BBT charting along with cervical mucus monitoring and/or OPK’s (ovulation predictor kits). The appearance of EWCM (egg white cervical mucus) is a very good indicator ovulation is close. When you see EWCM, it’s a good time to plan for intercourse if you want to conceive.

4. A note about using OPKs alone… Women with very regular cycles can usually rely on OPKs alone, though I suggest BBT charting or monitoring cervical mucus, too. Some women have a luteinizing hormone (LH) surge without ovulating. The LH surge is what OPKs detect. If your cycle is irregular or you’re over 40, you may want to use another ovulation tracking method besides OPK’s.

5. Your chances of conception each cycle are tied to many factors: overall fertility health, age, partner’s fertility, or presence of a challenge. On average, a woman in her late 30’s has about a 20-25% chance of conceiving per cycle. Try to be easy on yourself, patient and hang in there!

Important Reasons to Consider BBT Charting

Fertility charting/BBT charting has real advantages for women on the journey to conceive because it not only confirms ovulation, it also tracks your entire cycle. There is more to fertility health than just ovulation. BBT charting can tell whether the phases of your menstrual cycle are balanced, or whether you are ovulating earlier or later than expected.

Additionally, BBT charting doesn’t stop at ovulation. It follows the luteal phase of your menstrual cycle. An ideal luteal phase should last 12 or more days for the best conception and implantation chances. A short luteal phase or luteal phase defect may indicate low progesterone (a miscarriage risk factor), need for a diet change, or more vitamin B6.

Your BBT chart can also show signs of potential health concerns that can impact fertility health to review with your physician, for example, poor thyroid function. Staying informed on all of these factors, plus using a backup method for ovulation detection, offers the best opportunity for conception and understanding more about your own unique fertility health.

Are You Using a Fertility App?

Unfortunately, the latest research shows many women who are tracking their cycles with fertility apps or on the web may not be getting accurate results. A new study published in Obstetrics & Gynecology found that of the 53 top websites and smartphone apps the researchers analyzed only four accurately predicted the fertile window!

Take time to learn when you ovulate!

We certainly value and trust women’s intuition, yet when you are struggling to conceive, it’s best to eliminate the guesswork around ovulation and learn to detect the exact day it happens. You won’t regret it knowing your cycle this intimately now or in the future.


  • Kiefer, A. (2015, Feb.) Fertility in Your 30’s and 40’s: 7 Thing You Need To Know. Retrieved from:
  • Sifferlin, A. (2016, June). Why Your Period Tracker Is Wrong. Retrieved from:
  • Trying To Conceive Q & A. (2018). Retrieved from:
  • Karande, V. (2014, Aug.). Is The Best Time To Get Pregnant The Two Days Before Ovulation? Retrieved from:
  • Hsiu‐Wei Su, et al. (2017, Sept.). Detection of ovulation, a review of currently available methods. Bioengineeering and Translational Medicine; 2(3): 238–246. Published online 2017 May 16. doi: 10.1002/btm2.10058. Retrieved from:

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  1. Avatar

    Can you list the top 4 fertility apps that came up accurate? I use Fertility Friend and I am noticing that even when I think its wrong – its turning out to be right in terms of when to expect my period each month even when I have short cycles than usual. So I think FF is pretty accurate but I’d hate to think I’m BBT charting with an app that doesn’t even work.

  2. Avatar

    What is the best app to use?