Hormonal birth control definitely has several upsides, but many forms come with side effects that may leave you searching for nonhormonal options.
Are you curious about tracking ovulation to prevent pregnancy? Or maybe you’ve heard about using Fertility Awareness-based Methods (FABMs) as birth control, and you’re wondering whether FABMs are effective or not.
We explain whether tracking ovulation alone is effective to avoid getting pregnant, and break down the science on how FABMs work as birth control. So before you toss out your hormonal method, read up on this first.
To begin, some basics...
What’s my fertile window?
Your fertile window is the time when conception is possible. It’s the period when you need to abstain from sex or use a barrier method if you’re using a FABM for birth control.
You’ll commonly see the fertile window described as 6 days long. Years of science show nearly all pregnancies were conceived in a 6-day period: the five days before ovulation, and ovulation day itself (1).
Your fertile window is influenced by factors such as the lifespan of the egg and sperm, and the presence of fertile cervical mucus (CM) (2). Fertile CM, often described as egg white or watery CM, provides sperm with safe passage to the egg by creating a friendly alkaline environment (2) .
That said, your own fertile window is based on your fertility and how long your partner’s sperm survive. Sperm may die within minutes to hours in the vagina’s naturally acidic environment but may live 3-5 days in fertile CM (2).
You’re probably wondering, Why do I need to know about my fertile window? Can’t I just track ovulation to tell whether or not I’m fertile?
Can tracking ovulation prevent pregnancy?
Maybe you’ve seen urine-based ovulation prediction kits (OPKs) or you’ve started using one. OPKs to detect the surge of luteinizing hormone (LH) that signals ovulation, but OPK results may be misleading.
As the American Pregnancy Association notes, “Ovulation tests only identify the LH surge up to 24 to 48 hours before ovulation, and sperm can survive in the body up to 3 to 5 days. Therefore, if you have intercourse before you discover the LH surge, the egg could still be fertilized (3).” The organization advises against relying solely on ovulation tests to avoid getting pregnant. Read more about using LH for birth control here.
It’s also worth noting here that ovulation trackers (aka period tracking apps) typically rely on algorithmic guesses involving the average woman's cycle. If you’re like most women, you don’t ovulate on day 14 of your cycle (4). In one study, only 30% of women were found to even ovulate between day 10-17 (Wilcox). According to a recent massive study of more than 600,000 real-world menstrual cycles, the “widely held belief that ovulation occurs consistently on day 14 of the cycle is not correct (5).”
If OPKs aren’t reliable, what should you rely on? The Symptothermal Method involves tracking additional fertility signs like basal body temperature (BBT) and cervical mucus and is 99.6% effective with perfect use (12).
What's the Symptothermal Method?
The Symptothermal Method involves tracking your BBT, CM, and ideally one other fertility cue, cervical position. The position, openness, and firmness of your cervix changes during your cycle, and tracking these changes is another helpful sign to assess whether you’re in your fertile window or not (7). (More on cervical position here.)
The Symptothermal Method, per Toni Weschler’s leading book on fertility, Taking Charge of Your Fertility, is “considered the most comprehensive and reliable of all the natural methods because the two primary signs must corroborate each other before you are considered safe (7).”
BBT is your body’s resting temp. You take it daily at the same time each morning when you first wake up. BBT does not predict ovulation — it can only confirm ovulation has occurred. BBT typically rises 0.5 to 1°F when you ovulate and stays elevated until your period starts (Read up on BBT tracking here).
You may think — okay, why not just track my BBT? Science suggests tracking BBT is an unreliable method of ovulation detection (6). Plus as mentioned above, BBT does not tell you when you’re in your fertile window, it can only confirm the window has closed for that cycle.
To avoid getting pregnant, you’ll need to track both BBT and cervical mucus (and for extra precautions, cervical position) (10).
Cervical mucus is secreted by the glands in your cervix and serves multiple functions, including helping sperm reach the egg (11). Generally, CM starts out drier and less fertile after your period and becomes wetter and slippery as you enter your fertile window (7). It may look like raw egg whites or skim milk — signaling you’re fertile and need to avoid sex or use protection if you don’t want to get pregnant. (Quick note: Everyone’s CM is unique; learn more about evaluating different types of CM here)
If you’re tracking CM as a fertility sign, check your CM throughout the day because CM can sometimes take time to descend from the cervix through the vagina (7).
Is the Symptothermal Method effective birth control?
This method is highly effective birth control when used correctly. Most research shows the Symptothermal Method is one of the most accurate FABMs — as long as you track fertility signs daily AND avoid sex or use protection during your fertile window (8).
Two papers showed you have less than a 1% chance of getting pregnant if you follow the method to the letter, but another study showed “typical” users had pregnancy rates between 13-20% (8). Yikes.
Attempting to make sense of these vastly different results, researchers followed 900 German women who were using the Symptothermal Method over 13 months (9). They discovered much of the problem boiled down to couples having unprotected sex when they shouldn’t have (9).
Couples who had unprotected sex during the fertile window had pregnancy rates of 7.46% (9). But couples who skipped sex or used protection during the fertile window had pregnancy rates of only 0.43% or 0.59%, respectively (9).
What's the bottom line?
While you can track ovulation to prevent pregnancy, you also have to be willing to track fertility cues (BBT and CM at the very least) daily AND use protection or abstain from sex during the fertile window.
Of course, you always want to discuss your birth control options with your doctor, but bear in mind that some general practitioners may not be up-to-speed on FABMs.