Calendar method of contraception, or Knaus-Ogino method is one of the methods of natural family planning. The method is based on determination of the date of ovulation and abstinence from sexual intercourse in the fertile days. The fertile days are a phase of ovulation when a woman can get pregnant.
The calendar method is one of the most unreliable method of contraception with the Pearl Index from 9 to 40 (the number of pregnant women out of 100), so you should use another, more effective way to prevent pregnancy such as hormonal contraception or condoms. For adherents of the natural methods of contraception the best alternative is symptothermal method based on a more precise finding of ovulation days by monitoring changes in basal body temperature and consistency of cervical mucus.
For successful application of the calendar method of contraception, it should be maintained a calendar of menstrual cycles during one year. The calendar method is not suitable for women with irregular menstrual cycles because it is impossible to calculate in advance the date of ovulation, without the use of additional means.
By the method of Ogino-Knaus, the fertile (dangerous) days can be calculated by the formula: beginning of the fertile period = duration of the shortest cycle minus 18 days end of the fertile period = duration of the longest cycle minus 11 days
For example, observations over the last 12 cycles yielded the following results: the shortest cycle was 26 days, the longest - 32 days. Thus, days 8 to 21 of the cycle (1st day of the cycle is the first day of menstruation) are favorable for conception. In order to prevent pregnancy in these days a woman should refrain from sexual intercourse or to use additional methods of contraception such as condoms or spermicides. From the 1st to 8th day and from the 21st day till the end of the cycle it is possible to not use contraception.
On the basis of the calendar method, an Austrian gynecologist Mary Hengstberger developed a so-called birth control necklace for women from the third world countries who do not have money to buy contraceptives. This necklace consists of beads painted in different colors, with the number of beads equal to the average duration of cycles of the necklace owner. First 3-5 beads are painted in red and stand for menstruation. In the middle of the necklace there are blue beads (the association with water, fertility), indicating the days when you should abstain from sex. All other beads painted in yellow (drought) mean infertile period of the cycle. The necklace is worn with a small rubber ring, which should be moved every day to the next bead. Thus, a woman can recognize in which phase of the cycle she is now, and adjust her sexual life accordingly.
Also, there are very widespread computer programs which calculate the dangerous period on the basis of past cycles.
Two new birth control medications
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