OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What is the effectiveness of the combined pill in preventing pregnancy?

1. Approximately 80%

2. About 90%

3. Overall, 99%

4. Only 60%

The correct answer is: Overall, 99%

The combined pill is a highly effective form of contraception, with an overall effectiveness rate of approximately 99% when used correctly. This means that among typical users, less than one in 100 women will become pregnant in a year while using this method. The high effectiveness is primarily due to the hormones in the combined pill—estrogen and progestin—which work together to inhibit ovulation, thicken cervical mucus to prevent sperm from reaching the egg, and thin the lining of the uterus to reduce the likelihood of implantation if an egg were to be fertilized. While it's important to note that the effectiveness can decrease if pills are not taken consistently or if other medications interfere with their action, in general and with perfect use, the combined pill stands out as a very reliable option for preventing pregnancy.