When it comes to family planning—deciding how many children to have and how many years apart they’ll be spaced—women are faced with few choices. Among them: Condoms, IUDs or trading in your birth control for a lot less control.But a new study shows there’s another option, that’s side-effect free: A different take on the rhythm method. Yes, that form of pregnancy protection long vilified by your sex-ed teacher and your mother got a makeover. Meet “The Standard Days Method,” where you use a string of color-coded beads to identify your fertile days (rather than your math skills). The Standard Days Method has a perfect-use failure rate of about 5 percent—less than the rhythm method, and some condoms and diaphragms.A study, to be published in the October issue of Journal of Family Planning & Reproductive Health Care, followed 1,659 women who used the Standard Days Method. This method, which was created by researchers at the Institute for Reproductive Health at Georgetown University Medical Center, identifes the 12-day “fertile window” of our cycles. These days factor in the life of a woman’s egg (about one day), the viable life of sperm (about five days), plus the varied timing of ovulation from cycle-to-cycle.

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When used for a year, this method was found to be 95 percent effective at preventing pregnancy. Two-thirds of the women, almost all of whom had children under two, continued using the method effectively in the next two years.“Women choose to use this to achieve and avoid pregnancy. They like that it’s side-effect free. It works with their body and doesn’t squelch fertility,” says Institute for Reproductive Health Director Victoria Jennings, Ph.D., professor of obstetrics and gynecology at Georgetown University Medical Center.“This method includes a lot of women but not everybody,” she adds. For a large part, those who didn’t continue the method had cycles that fell outside the 26-32 day range.

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How does it work? Women identified the week of their cycle when they were most fertile, with “CycleBeads,” created by The Institute for Reproductive Health. Women moved a rubber band along one bead a day, starting with the red bead, which (you guessed it) signals your menstrual cycle.Once you hit the glow-in-the-dark beads (beads 8-19), you know you’re more likely to get pregnant upon having unprotected sex. When you reach the brown beads, pregnancy is very unlikely.

In year two, 2.8 percent of women had unplanned pregnancies, followed by 4.7 percent of women in year three.Overall, this fertility awareness program is beneficial for women trying to conceive a child and is as effective (if not more) as other birth control methods for those trying to avoid pregnancy. (Condoms are 98 percent effective at preventing pregnancy, when used correctly).Still, using a condom on top of a Standard Days Method would be a very safe bet against pregnancy and STDs for those who are not confident of the sexual history of their partner.

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And, for those who balk at the thought of holding off on sex 12 days per month, research shows this method won’t kill your sex life.“Essentially women using this method have sex just as often as other women, if not more often, but they tend to have sex more often on the non-fertile days,” Dr. Jennings says.