Operational Obstetrics & Gynecology

Rhythm Method

The rhythm method of contraception involves avoiding unprotected intercourse during the fertile time.

Ovulation occurs approximately 14 days prior to the onset of the menstrual flow.

For women with regular, predictable menstrual periods, this means that by avoiding unprotected intercourse around the time of ovulation, pregnancy can be prevented.

Fertilization must occur within 24 hours of ovulation to be successful. Sperm can appear at the end of the fallopian tube within 10 minutes of male orgasm and can remain there for at least 48 hours, sometimes longer.

For a woman with regular, predictable periods occurring every 28 days, avoiding unprotected intercourse from approximately day #9 through day #19 (5 days on either side of the expected ovulation) will provide reasonable protection against pregnancy (70-80%). Failures occur because of:

• Earlier than expected or later than expected ovulation.
• Sperm living longer than expected in the fallopian tube.

For women with longer menstrual cycle frequencies (32 days, for example), the days to avoid unprotected intercourse should be adjusted. For a 32-day cycle, ovulation usually occurs 14 days prior to menses, on day #18. This means avoiding unprotected intercourse from day #13 through day #23.

If fewer than 5 "off days" on either side of ovulation are used, this method will be less effective. If more than 5 "off days" are used, this method becomes more acceptable. It can never be 100% effective, however, since pregnancies have been recorded following intercourse on any day of the menstrual cycle.

If an annual failure rate of 20-30% is not acceptable, or if menstrual periods are irregular, other forms of contraception may prove more satisfactory.

Contents -  Introduction -  Medical Support of Women in Field Environments -  The Prisoner of War Experience -  Routine Care -  Pap Smears -  Human Papilloma Virus -  Contraception -  Birth Control Pills -  Vulvar Disease -  Vaginal Discharge -  Abnormal Bleeding -  Menstrual Problems -  Abdominal Pain -  Urination Problems -  Menopause -  Breast Problems -  Sexual Assault -  Normal Pregnancy -  Abnormal Pregnancy -  Normal Labor and Delivery -  Problems During Labor and Delivery -  Care of the Newborn

This web version of Operational Obstetrics & Gynecology is provided by The Brookside Associates.  It contains original contents from the official US Navy NAVMEDPUB 6300-2C, but has been reformatted for web access and includes advertising and links that were not present in the original version. This web version has not been approved by the Department of the Navy or the Department of Defense. The presence of any advertising on these pages does not constitute an endorsement of that product or service by either the Department of Defense or the Brookside Associates. The Brookside Associates is a private organization, not affiliated with the United States Department of Defense. All material in this version is unclassified.

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