But does it really prevent pregnancy? And is it right for you?
When you choose natural family planning, you're relying on your own fertility awareness -- knowing when you’re most likely to get pregnant.
Today, there are plenty of tools to assist you: high-tech digital thermometers, kits that measure certain hormones in your urine, and smartphone apps. Advances in science have given us a better understanding of fertility and ovulation. But it ultimately comes back to the basics.
"The most important thing to remember is that no matter what kind of assistance or tools someone uses, you have to understand the principles behind the method,” says Kenneth E. Johnson, DO, an OB/GYN at Nova Southeastern University’s College of Osteopathic Medicine in Fort Lauderdale, FL.
Typically, an egg releases from one of your ovaries every month. If your periods come every 28 days, you’ll ovulate about 14 days before the start of each period. After you ovulate, the egg can live for about 24 hours. Sperm can live for 7 days. If sperm is alive inside you while your egg is, you can get pregnant.
Your fertile days will most likely be from 5 days before to 3 days after ovulation.
You may have heard your mother or grandmother mention the rhythm or calendar method. It was created in the 1930s. With it, women chart out their periods on a calendar, and gauge which days they they're fertile using simple math.
Today, there are several other ways to predict when you can get pregnant:
Standard Days: This method is similar to the rhythm method. It still uses a calendar, but it relies on one basic rule: If your menstrual cycle is between 26 days and 32 days long, days 8 through 19 are your most fertile. That's when you shouldn't have sex. “It’s extremely rare that a woman always has 28- or 29-day cycles. Some variability is normal,” says Victoria H. Jennings, PhD, director of the Institute for Reproductive Health at Georgetown University in Washington, D.C.
If you know you have irregular periods, Standard Days might not be right for you. “There’s really no way to predict when ovulation happens in an irregular cycle,” says Nerys C. Benfield, MD, MPH, director of family planning at Albert Einstein College of Medicine in New York.
Cervical mucus: With this method, you pay attention to the mucus made by your cervix. Right before you ovulate, your cervix makes a lot of thin, slippery mucus that feels a lot like raw egg whites. Right after you ovulate, it doesn’t make as much, and it becomes thicker.
TwoDay: This is a more specific way of tracking your cervical mucus. You check for it at least twice a day. Did you see any that day or the day before? If so, you're probably fertile. If you go 2 days without noticing any, you’re less likely to get pregnant.
Basal body temperature (BBT): Your body’s temperature can rise between 0.5 and 1 degree when you ovulate and stay higher until the end of your menstrual cycle. You take your temperature every morning right when you wake up, before getting out of bed or having anything to eat or drink. The challenge with the BBT method is it tells you when ovulation has already happened. If you had sex a couple of days before, you may already be pregnant.
Symptothermal. This method combines others, usually cervical mucus and BBT. Using more than one can give you a stronger sense of what’s going on with your fertility.
But keep in mind other things can also cause changes in both your cervical mucus and temperature. “Infections, medications like antihistamines [like you would take for colds or allergies], medications for HIV, mood-altering drugs, antibiotics, and anti-inflammatories can affect both your temperature and secretions,” Jennings says.
The market is full of fertility-awareness apps that can help you keep track of your periods, cervical mucus, and temperature. “Apps are good things in that they alert women to the idea that they are not fertile all the time. But most of these apps are based on unknown algorithms and are largely untested as far as family planning is concerned," Jennings says.
That doesn’t mean they can't help, but you should do some research before you decide to use one, she says. And don't rely on it alone.
You can also buy kits at the drugstore to help you predict when you’re going to ovulate. They measure hormones levels in your pee or spit. Hormones surge about 36 hours before you ovulate.
These kits can be helpful for women who are considering natural family planning before they actually try it, Johnson says. “Using these kits for 3 months can help you see if you have a dependable cycle.”
But there’s a potential pitfall when it comes to family planning. “Kits are only going to tell you a day or so before. Sperm has a life span of up to 7 days. If you had sex 3 days ago and the ovulation kit says you’ll ovulate tomorrow, the sperm is already in your body and waiting," Benfield says.
So does natural family planning work? In theory, yes, with perfect use and a regular cycle. That means sticking to it every month, no exceptions.
“With correct use, Standard Days is 95% effective and TwoDay is 96% effective,” Jennings says.
But people aren’t perfect and nature isn’t always on schedule, Johnson says. “Regardless of how careful you try to be, you can ovulate with no signs or symptoms. There is good evidence that natural family planning to prevent pregnancy will not be better than 80% effective.”
According to the CDC, the typical failure rate is 24%. That means that when mistakes among all women who use natural family planning are accounted for, roughly 1 in 4 women who use it will get pregnant.
“It takes diligence and vigilance,” Benfield says. “When we look at a large group of women, the more diligence something takes, the less effective it is. But on an individual basis, it can be effective for a very dedicated woman.”
Is It a Good Choice for You?
Natural family planning may be a good option for women who know they can stick to the plan and those who have conditions that make other methods risky.
Talk with your doctor and decide together the best options for you.