Natural birth control methods do not rely on either hormones or contraceptive tools to prevent pregnancy; instead, these methods focus on identifying the days when a woman is ovulating and avoiding sexual intercourse for several days around that time. As research has shed more light on the science of ovulation and fertility, this form of birth control has become an increasingly popular and reliable way to prevent pregnancy.
Theory
Natural birth control methods that rely on identifying the fertile part of the menstrual cycle to prevent pregnancy are referred to as fertility awareness methods (FAMs). A woman who uses these methods must determine when she ovulates; combining that knowledge with an understanding of how long both an egg and a sperm can survive inside her body allows her to identify certain days during each menstrual cycle when intercourse is likely to result in pregnancy. The two main techniques which FAMs rely on for detecting fertile days include observing physiological changes and charting monthly cycles.
Physical Signs
The physiological indicators of fertility that a woman can observe as part of a natural birth control plan include basal body temperature, cervical mucus and cervical position. Basal body temperature spikes within 12 hours of ovulation, helping a woman identify when she is no longer in the fertile phase of her cycle. Cervical mucus changes throughout the cycle but is at its slickest and most slippery just before, during and after ovulation, according to the Feminist Women’s Health Center. The cervix is at its highest and most open position during ovulation.
Cycle Charting
Women who opt to use natural birth control but prefer not to monitor the physical signs of ovulation may instead chart their cycles. This method consists of recording the cycle length for several months, noting the longest and shortest cycles and applying a mathematical formula to determine which days the woman is likely to be fertile. Using this technique requires that she continuously chart her cycles since only cycles from the previous 12 months should be used.
History
During the 1930s, doctors noticed that women typically ovulated about 14 days before the start of their next menstrual period; the rhythm method of birth control was developed based on this early observation. In the 1950s, researchers discovered that subtle changes in cervical mucus and body temperature correlated with ovulation; finally, in the 1970s, doctors also noticed changes in the cervix during ovulation. Various forms of natural birth control were suggested to use some or all of these observations to predict ovulation and prevent pregnancy .
Effectiveness
For women who track the physical signs of ovulation, the effectiveness of the method depends on which ovulation cues they choose to follow, as well as their accuracy in identifying the changes that indicate they’re ovulating. Keeping track of all three fertility signs will allow for the more accurate ovulation prediction than relying on just one or two signs. Both forms of FAM are more effective in women with regular menstrual cycles; they also typically become more reliable the longer they’re used, according to the Feminist Women’s Health Center.
