Question

Describe the principal methods of contraception, including their methods of action, likely failure rates, and protection against STDs.

Short answer

The principal methods of contraception are: 1. Barrier Methods: These prevent sperm from reaching and fertilizing an egg and have failure rates of 2-15%. They include male and female condoms and diaphragms. These methods provide protection against most STDs. 2. Hormonal Methods: These methods use hormones to prevent ovulation or alter the uterus environment, and have effectiveness rates of 91-99%. They include birth control pills, patches, injections, vaginal rings, and implants. They do not provide protection against STDs. 3. Intrauterine Devices (IUDs): These are small devices inserted into the uterus that have effectiveness rates of over 99%. They come in hormonal and copper forms and do not protect against STDs. 4. Emergency Contraception: Used after unprotected sex or contraceptive failure, these pills have effectiveness rates of 75-89% and do not protect against STDs. 5. Natural Methods: Fertility awareness techniques have effectiveness rates of 76-88% and rely on monitoring menstrual cycles, basal body temperature, and cervical mucus. They do not provide protection against STDs.

Step-by-step solution

1. Barrier Methods

Barrier methods of contraception work by preventing sperm from reaching and fertilizing an egg. They include male condoms, female condoms, and diaphragms. Male and female condoms are made of latex, polyurethane, or polyisoprene and provide around 85-98% effectiveness, with failure rates of 2-15%. Diaphragms are made of silicone and used with spermicide; they have a failure rate of approximately 12% when used correctly. Barrier methods are the only type of contraception that also provides protection against most STDs, including HIV. The protection level depends on the correct and consistent use of the barrier method during each sexual encounter.

2. Hormonal Methods

Hormonal methods of contraception involve the use of hormones to prevent ovulation, thicken cervical mucus (which makes it more difficult for sperm to reach the egg), or alter the lining of the uterus. These methods include birth control pills, patches, injections, vaginal rings, and implants. Their effectiveness rates range from 91-99%, depending on the method and consistency of use. The protection against STDs is non-existent for hormonal methods, so using a barrier method like condoms in combination is recommended for protection against STDs.

3. Intrauterine Devices (IUDs)

IUDs are small, T-shaped devices inserted into the uterus by a healthcare professional. There are two types of IUDs: hormonal and copper. Hormonal IUDs release progestin, which thickens cervical mucus and reduces the likelihood of sperm reaching the egg, while copper IUDs release copper ions that are toxic to sperm and impair their ability to fertilize an egg. IUDs have a low failure rate, with effectiveness rates of over 99%. They do not provide protection against STDs and should be used with barrier methods for optimal protection.

4. Emergency Contraception

Emergency contraception is used after unprotected sex or contraceptive failure (like a condom breaking) to prevent pregnancy. The two main types are emergency contraceptive pills (also known as "morning-after pills") and the copper IUD. The emergency contraceptive pills are either progestin-only (levonorgestrel) or a combined progestin-estrogen (ulipristal acetate) pill. The effectiveness of emergency pills ranges from 75-89%, depending on the type and how quickly it is taken after unprotected sex (within 72 hours for levonorgestrel and within 120 hours for ulipristal acetate). Emergency contraception does not provide protection against STDs.

5. Natural Methods

Natural methods of contraception involve tracking fertility signs such as menstrual cycles, basal body temperature, and cervical mucus to determine the fertile days, and either abstaining from sex or using barrier methods during those days. These methods have a varying degree of effectiveness, ranging from 76-88% based on different fertility awareness techniques, such as the Standard Days Method, the Sympto-Thermal Method, and the Cervical Mucus Method. Natural methods do not provide protection against STDs, and using barrier methods during fertile days is necessary for those who want to prevent the transmission of infections.

Key concepts

Barrier Methods

Barrier methods are a popular choice for many because they physically block sperm from reaching the egg. This category includes items like male and female condoms and diaphragms.
Male condoms are often made from latex, but alternatives such as polyurethane or polyisoprene are available for those with allergies.
Female condoms provide a similar barrier but are inserted into the vagina. Diaphragms, on the other hand, are placed over the cervix and used with spermicide to enhance effectiveness. The effectiveness of these methods ranges between 85% to 98%, largely dependent on correct and consistent use.
A key advantage of barrier methods is their ability to offer protection against sexually transmitted diseases (STDs), including HIV.

• Effectiveness: 85-98%
• Failure rate: 2-15%
• Protection against STDs: Yes

Hormonal Methods

Hormonal contraception is widely used for its high effectiveness in preventing pregnancy by regulating the hormones involved in the reproductive process. Birth control pills, patches, injections, vaginal rings, and implants fall under this category.
These methods work by stopping ovulation, thickening cervical mucus, and altering the uterine lining, making it harder for sperm to reach the egg or for a fertilized egg to implant. The effectiveness is quite high, ranging from 91% to 99% with perfect use, but they do offer no protection against STDs.
Combining hormonal methods with barrier methods can provide both effective birth control and STD protection.

• Effectiveness: 91-99%
• Protection against STDs: No

Intrauterine Devices (IUDs)

IUDs are small, T-shaped devices placed inside the uterus by a healthcare provider. There are two main types: hormonal and copper.
The hormonal IUD releases a type of progestin to prevent sperm from reaching the egg, while copper IUDs release copper ions, creating an environment toxic to sperm. IUDs are known for their high effectiveness, with rates over 99%.
However, like hormonal methods, they do not protect against STDs.
Using condoms in combination with IUDs is advisable for STD prevention.

• Effectiveness: >99%
• Protection against STDs: No

Emergency Contraception

Emergency contraception provides a crucial backup for preventing pregnancy after unprotected sex or contraceptive failure. Two main forms exist: emergency contraceptive pills and the copper IUD.
The pills are most effective when taken as soon as possible after the incident, with levonorgestrel being effective up to 72 hours and ulipristal acetate up to 120 hours. The effectiveness ranges from 75% to 89% depending on how quickly they are taken.
However, they do not protect against STDs, so safety practices like using condoms should remain consistent.

• Effectiveness: 75-89%
• Timeframe: 72-120 hours after intercourse
• Protection against STDs: No

Natural Contraception Methods

Natural methods rely on tracking natural fertility signals to avoid pregnancy. Techniques include monitoring menstrual cycles, checking basal body temperature, and observing cervical mucus changes.
Some commonly known methods include the Standard Days Method, the Sympto-Thermal Method, and the Cervical Mucus Method. These methods require a thorough understanding and consistent monitoring, with effectiveness ranging from 76% to 88%.
Because they offer no STD protection, using barrier methods during fertile periods is recommended for those at risk of STDs.

• Effectiveness: 76-88%
• Protection against STDs: No