When predicting ovulation, the difference between the calendar method and the Clearblue Digital Ovulation Test is that the digital test detects the surge in luteinising hormone (LH) that triggers ovulation. I found a research study that analysed the Clearblue Digital Ovulation Test and the calendar method, it showed that the ovulation test is far more accurate.
The Clearblue Digital Ovulation Test is available on Amazon – and the least expensive way to buy it is in the 20 pack (which is also the most accurate way to predict your most fertile days, because you’ll be consistent).
The calendar method doesn’t help you identify variabilities in your menstrual cycle. So, if you try to predict ovulation according to the dates on your calendar and the day you started your last menstrual cycle, you won’t get information about your LH hormone level.
Digital Ovulation Tests vs. Calendars
“We undertook a comparative analysis of the two methods – calendar and the Clearblue Digital Ovulation test – using a group of 101 women recruited via local press adverts and a website,” says Dr. Jayne Ellis, Director of Scientific and Medical Affairs at SPD Swiss Precision Diagnostics GmbH, Geneva, Switzerland. “The women collected a total of 895 daily urine samples. Ovulation was confirmed by using laboratory analysis of the LH surge, combined with a progesterone rise in the urine. This is a clinically validated method of confirming ovulation.”
Note that Swiss Precision Diagnostics is the company that actually made the Clearblue Digital Ovulation test. This doesn’t mean that their research results are less accurate or invalid, but it does mean they have a vested interest in finding that the the Clearblue Digital Ovulation test is a more accurate predictor of ovulation than the calendar method.
The calendar method predicted ovulation correctly in only one in four women, whereas the Clearblue Digital Ovulation test predicted correctly in 99% of women over the same period.
The Clearblue Digital Ovulation test consists of a digital reader and urine test sticks, which could detect the surge in luteinising hormone (LH) that triggers ovulation. According to this company, using a widely available ovulation test such as the Clearblue is a more reliable method of predicting when a woman will be at her most fertile, when compared to the commonly used calendar method. Researchers said that the ovulation test could cope with cycle variability, whereas the calendar method could not.
“The test stick is held in the urine stream,” says Dr Ellis. “If the LH levels are elevated, a smiley face appears on the screen. This indicates that the woman is in a highly fertile phase. If there is no hormone surge, a circle is shown on the screen and the woman can test again the following day.”
To learn more about predicting ovulation, read 3 Types of Ovulation Predictor Kits and How They Work.
The calendar method of predicting ovulation uses the previous cycle length and subtracts 14 or 15 days to give an estimate of the day of ovulation. It’s the most commonly used technique for predicting fertility. Calendar and fertility apps are available on many websites and now on mobile phone applications – which I described in Fertility App to Help Women Get Pregnant. The calendar method is used by 35% of those attempting to conceive.
However, up until now the calendar method had not been subjected to scientific scrutiny, and had not been compared to the Clearblue Digital Ovulation Test in terms of predicting the best times to get pregnant.
The calendar method is less effective in predicting ovulation and peak fertile days because it uses data from previous cycles. Menstrual cycles are naturally variable in many women. Cycle length in the study ranged from 14 to 50 days. The researchers found that use of the calendar method in women trying to conceive resulted in only one third of cycles where peak fertile days were correctly predicted. On an individual basis only one in four women trying to conceive would have correctly identified their peak fertile days using the calendar method. In 48% of cycles, the peak fertile period was identified by this method after it had occurred.
If your periods are irregular and you want to use the calendar method to predict ovulation, read 8 Natural Ways to Regulate Your Period.
By contrast, the Clearblue Digital Ovulation Predictor Tests would have been conducted on the day of the LH surge in 77% of the cycles if a seven-stick pack had been used and start day was based on average cycle length. In 6% of cycles the surge had occurred before the first test day, and in 17% of cycles it had occurred after the last test was conducted. However, if a 20-stick pack was used, a test would have been conducted on the day of the LH surge in 99% of cycles.
“Like the calendar method, the Clearblue Digital Ovulation Test is safe and non-invasive,” says Dr. Ellis. “But the difference is that it predicts ovulation accurately and therefore gives couples who want to get pregnant the chance to time intercourse correctly and maximise the chances of conception.”
Previous research has shown that 46% of cycles in women aged from 18 — 40 vary by seven days or more, and that this variation increases as women approach the menopause. At a time when more and more women are delaying pregnancy until their thirties, it is increasingly important that they have a better understanding of their own menstrual cycles and the days on which they are fertile.
If you haven’t gotten pregnant after six months of using an accurate product such as the Clearblue Digital Ovulation test, then you or your partner may have be an underlying fertility issues that should be investigated. Read 5 Signs You Should See a Fertility Doctor for help figuring out if you need to go beyond calendars and digital tests to predict ovulation and get pregnant.
What do you think of this research that compares the Clearblue Ovulation Predictor test with the calendar method of predicting fertile days?