Controlling Fertility: Contraception and Assisted Reproduction

Other hormonal methods include the progestogen-only pill, implant, injection and intrauterine system (IUS). Progestogen can thicken the mucus at the cervix, making it difficult for sperm to enter the uterus. It can also thin the uterine lining; some methods suppress ovulation too. The exact combination of effects depends on the method, so not every hormonal contraceptive works in precisely the same way.

An implant releases hormone from a small device beneath the skin. An injection delivers hormone that acts over an extended period. An IUS is fitted inside the uterus and releases progestogen. These methods avoid having to remember a pill every day. An IUS is hormonal, whereas a copper IUD is not.

How barrier methods prevent pregnancy

An external condom is a sheath worn over the penis. It collects semen, preventing sperm from entering the vagina. An internal condom is placed inside the vagina and forms a barrier to sperm. Condoms also help protect against sexually transmitted infections (STIs), an important advantage that hormonal contraception does not provide.

A diaphragm or cap covers the cervix, preventing sperm from entering the uterus. It is used with spermicide, a substance that kills sperm. Barrier methods do not alter the hormonal control of the menstrual cycle: ovulation can still occur, but sperm are prevented from reaching the egg.

Comparing effectiveness and practical advantages

Perfect use means using a method correctly every time. Typical use includes everyday mistakes, such as forgetting a pill or a condom slipping off. This distinction explains why a method can work very well biologically but be less effective in everyday life.

The figures below describe pregnancy prevention over the first year of use.

For example, 91% effectiveness means that about 9 out of every 100 users experience an unintended pregnancy within a year. It does not mean the method fails in 9% of acts of intercourse.

Evaluation means weighing these differences against a person's needs. An implant may be preferable when reliable pregnancy prevention without daily remembering is the priority. A condom has the additional advantage of STI protection. Using a condom alongside a hormonal method can address both needs; there is no single method that is best in every situation.

Clomifene therapy — Higher tier

Infertility can have several causes. One is insufficient reproductive hormone stimulation, so eggs do not mature or are not released regularly. Assisted reproductive technology (ART) uses medical treatments to help people conceive.

Clomifene is a fertility drug that causes more FSH and LH to be released. FSH stimulates egg maturation, and LH stimulates ovulation. If an egg is released, fertilisation may then occur inside the body following intercourse.

Clomifene therefore encourages the egg maturation and ovulation that the combined contraceptive pill prevents. It does not guarantee pregnancy, and stimulating the ovaries can cause several eggs to be released, increasing the chance of a multiple pregnancy.

IVF — Higher tier

In vitro fertilisation (IVF) involves fertilisation outside the body. It can help when fertilisation is difficult to achieve naturally, including some problems affecting either partner's fertility.

1. Hormone treatment involving FSH and LH stimulates the ovaries so that several eggs mature and reach the stage needed for collection.
2. The eggs are collected and mixed with sperm in a laboratory, where fertilisation can occur.
3. Fertilised eggs divide and develop into embryos.
4. One or sometimes two embryos are transferred into the uterus. Pregnancy can develop if an embryo implants in the uterine lining.

Stimulating several eggs provides more opportunities for fertilisation and embryo development, but IVF does not guarantee a pregnancy. Treatment can be physically demanding and unsuccessful attempts can be emotionally distressing. Transferring more than one embryo increases the possibility of a multiple pregnancy. These limitations help explain why producing embryos and achieving a successful pregnancy are not the same outcome.

• External/internal condoms: prevent sperm reaching the egg and help protect against STIs.
• Diaphragm/cap: covers the cervix; used with spermicide.
• Barrier methods do not change the menstrual cycle.
• Compare effectiveness, correct-use demands, convenience and STI protection.
• Typical use: implant/IUS over 99%, injection 94%, pills 91%, external condom 82%. Perfect-use effectiveness is higher for methods affected by user error.

ART — Higher tier

Clomifene: increased FSH/LH release → egg maturation and ovulation → fertilisation may occur inside the body.

IVF: FSH/LH treatment → several eggs mature → eggs collected → fertilisation in the laboratory → embryos develop → embryo transfer into the uterus.

Neither treatment guarantees pregnancy. Multiple eggs or transferred embryos can increase the chance of a multiple pregnancy.