Evaluation needs a supported judgement
Definition
Contraception
A method used to prevent pregnancy, either by using hormones or by stopping sperm reaching an egg.
- Effectiveness is the proportion of users for whom a method prevents pregnancy over the stated time and under the stated conditions.
- A comparison should also consider side effects, ease of correct use, reversibility, medical suitability and protection from sexually transmitted infections.
- The best method depends on the needs and circumstances in the question, so a conclusion must be supported by relevant evidence.
- When data are given, compare methods over the same time period and check whether the figures describe perfect use or typical use.
Exam technique
- Use evidence from the table or graph rather than listing memorised advantages.
- Balance a benefit against a limitation, then make a judgement that matches the person described.
Hormonal methods have trade-offs
- Hormonal methods can be highly effective because they prevent ovulation and may also thicken cervical mucus.
- Implants and injections are less affected by forgetting than a daily pill because they release hormone for a longer period.
- Possible disadvantages include headaches, nausea, mood changes, irregular bleeding and, for some combined methods, a small increased risk of blood clots.
- Hormonal methods do not protect against sexually transmitted infections and may be unsuitable for some people after medical assessment.
- Most hormonal methods are reversible, but normal fertility may take time to return after some injections.
Barrier methods block sperm
- Barrier methods, including condoms and diaphragms, physically prevent sperm from reaching an egg.
- They do not alter hormone concentrations, so they avoid hormone-related side effects.
- Condoms reduce the transmission of sexually transmitted infections as well as reducing the chance of pregnancy.
- Their effectiveness depends on correct use every time, and a condom can tear, slip or be put on incorrectly.
- A diaphragm must be positioned correctly over the cervix and is usually used with spermicide.
Example
- A table gives method A an effectiveness of 99%99\%99% and method B an effectiveness of 82%82\%82% under the stated conditions.
- The pregnancy percentages are 100%−99%=1%100\%-99\%=1\%100%−99%=1% for A and 100%−82%=18%100\%-82\%=18\%100%−82%=18% for B.
- If B is a condom and protection from sexually transmitted infections is required, B may still be the better choice despite its lower pregnancy prevention figure.
Data must match the person
- A person who cannot use oestrogen may need a progesterone-only or barrier method even if another method has a higher quoted effectiveness.
- A person who wants long-term contraception may prefer an implant because it does not require action at every episode of intercourse.
- A person who needs protection from sexually transmitted infections should use condoms because hormonal methods do not provide that protection.
- A strong evaluation states the choice, supports it with data, acknowledges a relevant drawback and explains why the benefit outweighs that drawback.
Self review
- Which factors should be considered besides effectiveness?
- Why are long-acting hormonal methods less affected by forgetting?
- What is one advantage and one limitation of barrier methods?
- How should a final judgement use the data and the person's circumstances?
