Fertility treatments use hormones and assisted reproductive technology to help people conceive. The most common is IVF: eggs are collected after hormone stimulation, fertilised in a laboratory, and the resulting embryo is transferred to the uterus. FSH and LH are the key hormones used to trigger egg development and release.
What causes infertility?
Infertility is defined as the inability to conceive after 12 months of regular unprotected intercourse. It affects approximately 1 in 7 couples in the UK. Common causes include:
| Cause | In women | In men |
|---|---|---|
| Hormone imbalance | Low FSH → eggs do not mature; irregular ovulation | Low testosterone → reduced sperm production |
| Physical blockage | Blocked or damaged fallopian tubes (often from infection) | Blocked sperm ducts |
| Age | Egg quality and quantity decline from mid-30s | Sperm motility and count may reduce with age |
| Other | Endometriosis; polycystic ovary syndrome (PCOS) | Low sperm count; abnormal sperm shape |
Understanding the cause determines which treatment is most appropriate.
What hormones control the menstrual cycle and why do they matter for fertility treatment?
In a normal menstrual cycle:
- FSH (follicle-stimulating hormone) is released by the pituitary gland and stimulates a follicle in the ovary to mature, producing an egg. It also stimulates the follicle to produce oestrogen.
- LH (luteinising hormone) surges mid-cycle and triggers ovulation — the release of the egg from the follicle.
Women who do not produce enough FSH may not develop mature eggs and will not ovulate. Giving them FSH as a fertility drug stimulates the ovaries to develop follicles and prepare eggs for release. This is the hormonal basis of both simple ovulation induction and IVF.
How does IVF work step by step?
In vitro fertilisation (IVF) ("in vitro" = in glass) fertilises eggs outside the body:
- Superovulation: the woman is given high doses of FSH to stimulate the ovaries to mature multiple eggs simultaneously (normally only one egg matures per cycle).
- Monitoring: ultrasound scans monitor follicle development.
- Egg collection: a thin needle is passed through the vaginal wall (guided by ultrasound) to collect the mature eggs from the ovarian follicles.
- Sperm preparation: a semen sample from the partner (or donor) is prepared, selecting the most motile sperm.
- Fertilisation: eggs and sperm are mixed together in a laboratory dish containing a culture medium that mimics conditions in the fallopian tube. Alternatively, a single sperm can be injected directly into an egg (ICSI — intracytoplasmic sperm injection) if sperm count or motility is very low.
- Culture: fertilised eggs (zygotes) are kept in an incubator at 37 °C for 2–5 days, during which they divide to form embryos of 4–8 cells.
- Embryo selection: embryos are assessed for quality; healthy embryos are selected.
- Embryo transfer: one or two embryos are placed into the uterus through a thin catheter. Additional embryos may be frozen for future attempts.
- Implantation: if successful, an embryo implants in the uterine wall and pregnancy begins.
The success rate in the UK is approximately 25–30% per IVF cycle for women under 35, falling with age.
What are the risks and limitations of IVF?
- Multiple births: if two embryos are transferred and both implant, twins result. Multiple pregnancies carry higher risk of premature birth and complications for both mother and babies.
- Ovarian hyperstimulation syndrome (OHSS): high FSH doses can over-stimulate the ovaries, causing pain, swelling, and, in rare cases, life-threatening complications.
- Emotional and physical burden: the hormone injections, monitoring appointments, egg collection, and waiting are demanding.
- Cost: IVF costs approximately £3,000–£5,000 per cycle privately; NHS funding is limited and varies by region.
- Embryo surplus: superovulation typically produces more embryos than are used; surplus embryos are frozen, donated to other couples, used in research, or destroyed.
What are the ethical arguments for and against IVF?
Arguments in favour of IVF:
- Enables people who cannot conceive naturally to have children, which many regard as a fundamental human desire.
- Surplus embryos can be donated to infertile couples or used in research to advance understanding of genetic diseases.
- IVF allows pre-implantation genetic diagnosis (PGD) to screen embryos for serious inherited conditions before transfer.
Arguments against IVF:
- Many surplus embryos are destroyed, which some religious traditions consider morally equivalent to ending a human life.
- Multiple births increase the risk of premature delivery and disability.
- The process is expensive and emotionally draining, with no guarantee of success.
- Critics raise concerns about the possibility of selecting embryos for non-medical traits ("designer babies").
Frequently asked questions
Why is FSH given at higher doses in IVF than in simple ovulation induction?
In IVF, the aim is to collect multiple mature eggs in a single cycle so that several embryos can be created, giving the best chance that at least one will implant successfully. Normal FSH levels mature only one follicle per cycle. High-dose FSH injections overcome the natural selection process that causes all but one follicle to stop developing, stimulating multiple follicles to maturity simultaneously. This "controlled ovarian hyperstimulation" is the key difference between simple fertility hormone treatment (which aims for natural ovulation) and IVF preparation.
What is the difference between IVF and ICSI?
In standard IVF, thousands of sperm are placed together with each egg in a culture dish, and fertilisation occurs when a sperm penetrates the egg naturally. In intracytoplasmic sperm injection (ICSI), a single sperm is selected under a microscope and injected directly into the egg using a fine needle. ICSI is used when the male partner has a very low sperm count, poor sperm motility, or abnormal sperm shape that would make natural fertilisation in the dish unlikely. The rest of the IVF process (embryo culture, transfer) is identical.
What happens to unused frozen embryos?
At the time of freezing, couples make decisions about the fate of any surplus embryos. Options include: storing them for personal future use (typically for up to 10 years under UK law, extendable with consent); donating them to another couple who cannot produce their own embryos; donating them to research (to study early human development or genetic diseases); or allowing them to perish (they are removed from storage and disposed of). The decision is personal and can be ethically complex, particularly for those who hold the view that a fertilised embryo has moral status from the moment of fertilisation.
Can hormones alone (without IVF) treat infertility?
Yes, for some causes. Women who do not ovulate because of low FSH levels can be given FSH injections or tablets that stimulate FSH production (such as clomifene citrate), triggering ovulation without egg collection or laboratory fertilisation. If fertilisation can occur naturally (the fallopian tubes are unblocked and the partner's sperm count is normal), this simpler treatment may be sufficient. IVF is chosen when sperm count is very low, tubes are blocked, or other treatments have failed.
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