Natural family planning, or Fertility Awareness Methods (FAM), is being used again by women who are looking for a birth control method with no side effects.
FAM is a system where women carefully predict their likely fertile days based on the lengths of their cycles, reported CNN.
When a woman ovulates, her basal body temperature (the body's temperature throughout the day) rises and she experiences wetness. Her cervix also changes positions based on whether or not she has ovulated.
"It's a process of becoming aware of the signals your body is giving you and keeping track of them," Ilene Richman, director of the Fertility Awareness Center, explained to CNN.
The CDC and the American College of Obstetricians and Gynecologists claim that FAM is the least successful form of birth control.
"You hear about 25 percent,1 in 4, who use it correctly can expect to get to get pregnant," Dr. Nathaniel DeNicola, an OBGYN with the University of Pennsylvania Health System, told CNN.
Supporters of the FAM birth control method say these statistics aren't accurate, as they often include women who skip a day of calculations.
"The perfect use rate is 99.6%-99.4% which is really good," Sarah Bly, a fertility awareness instructor, told CNN. ("Perfect use" is referring to women who are very particular about keeping their health statistics and don't miss a single day.) "A lot of statistics that (the doubters quote) are typical use, which include women taking risks," Bly says.
A German study from 2007 that tracked 900 women over 20 years consistently using FAM methods supports Bly's statement. The study found that only 2 percent of those women had an unintended pregnancy.
The issue with FAM is that the calculations must be precise and they must be done every single day. Some women say they are turning back to this old style of birth control because today's technology makes it easier to be precise.
New women's health apps - such as Kindara, Glow, and Ovuline - help with the calculations for women using FAM.
Aisha Mukooza, 25, started using FAM because she didn't like the side effects hormonal birth control had on her body, reported CNN. Now, she keeps a thermometer under her pillow and tracks the temperatures with Kindara.
"I'm a healthy person. I try to eat healthy food, so the idea of being pumped with synthetic hormones didn't appeal to me, in fact, it was scary," Mukooza told CNN.
Studies show some 4 out of 5 American women use hormonal birth control. At the same time, nearly 30 percent of all users stop using the pill because of side effects - including nausea, weight gain, sore or swollen breasts, spotting and mood changes.
The bottom line - FAM is growing popularity for women who are wary of the effects of hormonal birth control, even though it's not always easy to stay on top of the precise calculations that come with it.
"For the right patient, who is really willing to track the days, and are willing to track the temperature," DeNicola told CNN.
