Final answer:
The less effective form of birth control discussed is a behavioral method, specifically fertility awareness. This requires awareness of the menstrual cycle to avoid unprotected intercourse during the most fertile days. While it does offer some protection, its typical failure rate is between 20 to 25 percent.
Step-by-step explanation:
Behavioral Methods of Birth Control
The question refers to a less effective form of birth control that relies on the awareness of the woman's menstrual cycle. This is known as a behavioral method of contraception, specifically, fertility awareness methods. These methods include monitoring basal body temperature, cervical mucus characteristics, and avoiding unprotected vaginal intercourse during the most fertile days of the menstrual cycle. Fertility awareness methods are not as reliable as hormonal methods, IUDs, or barrier methods, and require daily motivation and strict tracking to improve effectiveness. However, their typical-use failure rates are at least 20 to 25 percent, making them less dependable.
Compared to hormonal methods that prevent ovulation, and IUDs that create an inflammatory condition in the uterus, behavioral methods are significantly more susceptible to user error and hence are considered the least effective form of contraception. While they do provide some level of protection against pregnancy, the success of fertility awareness methods highly depends on correctly identifying the fertile window and strictly abstaining from unprotected sex during that period.