Physiological basis and efficacy
Natural family planning is based on knowledge of the lifespan of germ cells. Sperm remain active on average for up to 4 days, while the oocyte released from the ovary lives for no more than 24 hours.
The main drawback of natural methods is their low contraceptive reliability. The Pearl Index (number of pregnancies per 100 women over a year of using the method) ranges from 6 to 40. This significantly limits their application. Furthermore, none of the natural methods protect against sexually transmitted infections (STIs).
Methods for calculating the fertile period
- Calendar (rhythm) Ogino-Knaus method
Based on mathematical calculation of the day of ovulation. With a regular 28-day cycle, ovulation occurs on day 14 (± 2 days). Taking into account the lifespan of sperm and oocyte, the fertile (unsafe) period lasts from cycle day 8 to 17. If the cycle is irregular, the duration of at least the last 6 cycles is analyzed. The beginning of the fertile window is calculated using the formula: shortest cycle minus 18 days. The end of the window: longest cycle minus 11 days. The method is unsuitable for significant cycle fluctuations, as virtually the entire month becomes "unsafe".
- Temperature method
Based on determining ovulation by the jump in rectal (basal) temperature. The fertile period is considered to be from the onset of menstruation until three days have passed after the temperature rise. The main drawback is the need for prolonged abstinence, which is inconvenient for an active sex life.
- Cervical mucus method
In the preovulatory phase, the volume of cervical mucus increases and it becomes more stretchy. Conception is most likely 2 days before the appearance of characteristic discharge and for 4 days after. The method is contraindicated in inflammatory processes in the vagina.
- Symptothermal method
A comprehensive approach where the patient simultaneously monitors rectal temperature, cervical mucus properties, and records the presence of ovulatory pain. It allows for the most accurate calculation of fertile days, but requires high persistence and meticulousness.
Coitus interruptus
Belongs to natural contraception options. Its main advantages are absolute simplicity and lack of material costs. However, the contraceptive efficacy of this method remains extremely low.
Mechanical (barrier) methods as an alternative
Unlike natural methods, barrier devices physically prevent sperm from entering the vagina or cervix. They have no systemic effect on the body, and condoms additionally provide protection against STIs (although they do not rule out the risk of infection with syphilis or viral infections through damaged skin contact).
Mechanical devices include:
- Male condoms. They are put on the erect penis. They must be removed strictly before the loss of erection to prevent slipping. Reliability is reduced when using oil-based lubricants (which destroy latex), improper storage, or vigorous sexual intercourse.
- Female condoms. Polyurethane film cylinders with two rings. The inner ring is placed over the cervix, the outer ring remains outside. Designed for single use.
- Vaginal diaphragm. A dome-shaped latex device with a flexible rim. Inserted before intercourse so that the dome covers the cervix. Reusable, but requires the mandatory use of spermicides. Removed no earlier than 6 hours and no later than 24 hours after intercourse.
- Cervical caps. Metal or latex cups placed directly over the cervix. Used with spermicides, removed after 6–8 hours (maximum 24 hours).
Diaphragms and caps do not protect against infections and have a number of contraindications: inflammation, cervical diseases, vaginal wall prolapse.
Indications and the "Double Dutch method"
Barrier contraception is indicated for casual encounters, infrequent sexual activity, and high risk of infection. To achieve maximum safety, the "Double Dutch method" is used. It involves the simultaneous use of a condom (for infection protection) and a highly effective method of contraception, such as hormonal or intrauterine (for reliable pregnancy protection).
Briefly: answers to topical questions
What is the mechanism of action of spermicides used in combination with barrier methods?
The mechanism of action of spermicides is the destruction of the sperm cell membrane. Chemical contraceptives cause the death of male germ cells upon intravaginal administration.
- Benzalkonium chloride — destroys the sperm cell membrane, exhibiting contraceptive properties immediately or after the formulation dissolves.
- Nonoxynol-9 — a spermicidal agent lethal to spermatozoa.
The drugs possess bactericidal and virucidal properties, but increase the permeability of the vaginal wall.
Which hormone causes the rise in basal temperature after ovulation?
The rise in basal temperature after ovulation is caused by the thermogenic effect of the hormone progesterone.
- Progesterone (corpus luteum produces this hormone) — acts on the thermoregulation center in the hypothalamus, causing the temperature to rise above 37.0 °C in the second phase of the menstrual cycle.
Hormone secretion is carried out by the corpus luteum of the ovary throughout the luteal phase. With the regression of the corpus luteum before the next menstruation, the hormone level drops, which is accompanied by a premenstrual decrease in basal temperature.
Which sexually transmitted infections do condoms not provide complete protection against?
Condoms do not provide complete protection against syphilis and viral diseases. High barrier protection does not rule out infection in the following cases:
- Syphilis — transmitted through contact with damaged skin areas of partners.
- Viral diseases — infection of partners is possible through contact with damaged skin areas.
Other mechanical barrier devices, such as the vaginal diaphragm and cervical caps, are completely devoid of protective action against sexually transmitted infections.
To calculate the fertile window in an irregular cycle (Ogino-Knaus method), remember the "18–11" rule: subtract 18 from the shortest cycle (start of unsafe days), and 11 from the longest (end).
Class and exam questions
Can the calendar method be used with irregular menstruation?
The method is extremely ineffective with significant cycle fluctuations. In such cases, the calculated fertile window stretches across almost the entire month, requiring continuous abstinence.
How long can the vaginal diaphragm be left in place after intercourse?
The diaphragm should be removed no earlier than 6 hours, but no later than 24 hours after sexual intercourse. With repeated contact after 3 hours, an additional application of spermicide is required.
What is the «double Dutch method»?
This is the combined use of a condom (for STI protection) and a highly effective method, such as hormonal or intrauterine contraception (for reliable protection against unwanted pregnancy).
What else to study on this topic
- Contraindications to the use of vaginal diaphragms and cervical caps
- Rules for caring for reusable barrier devices
- Effect of oil-based lubricants on the integrity of latex condoms
- Allergic reactions to latex: alternative contraception options
- Limitations of the temperature method during active sexual life
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