---
title: "In vitro fertilisation"
slug: "in-vitro-fertilisation"
type: "technology"
status: "established"
horizon: "present"
trl: 9
categories: ["reproduction", "society"]
tags: ["reproduction", "ivf", "embryo selection", "fertility", "regulation", "bioethics"]
summary: "The routine clinical procedure in which eggs are fertilised outside the body and an embryo is transferred to a uterus, and the platform every other embryo technology is built on."
updated: "2026-07-28"
humanEvidence: "Between ten and thirteen million children had been born after assisted reproduction by 2018 and several million since; live-birth rates fall steeply with the age of the egg, and birth defects are modestly more common than after natural conception."
access: "Available in most countries with a fertility sector but funded unevenly: NHS-funded cycles fell from 35 percent of UK treatments in 2019 to 27 percent in 2023, and a self-funded cycle costs several thousand pounds or dollars before optional extras."
reversibility: "irreversible"
issues: ["Cost figures are given for the UK only; a comparable US and international picture is missing."]
---

```infobox
{
  "caption": "Assisted reproductive technology",
  "rows": [
    { "label": "First live birth", "value": "1978, Oldham, England" },
    { "label": "Developed by", "value": "Robert Edwards, Patrick Steptoe" },
    { "label": "Nobel Prize", "value": "Medicine, 2010" },
    { "label": "Children born", "value": "10–13 million by 2018" },
    { "label": "Share of UK births", "value": "1 in 32 (2023)" },
    { "label": "Key variants", "value": "ICSI, frozen transfer, PGT" },
    { "label": "UK regulator", "value": "HFEA" }
  ]
}
```

**In vitro fertilisation** is the procedure in which eggs are recovered from ovaries, combined with sperm in a laboratory dish, cultured for a few days, and transferred to a uterus as an embryo. It is the oldest and most-performed of the assisted reproductive technologies, and it matters far beyond infertility medicine: almost every technique this wiki covers under reproduction, from [[embryo-selection]] to [[germline-editing]], is an operation performed on an embryo that only exists because of IVF.

## How a cycle works

A cycle runs in four steps: stimulation, egg collection, fertilisation and culture, transfer. Injected gonadotrophins stimulate the ovaries to mature many follicles at once rather than the single one of a natural cycle; ultrasound and blood hormone measurements track the response; and eggs are collected under sedation by a needle passed through the vaginal wall. In the laboratory the eggs are either mixed with prepared sperm, or, where sperm quality is poor, injected one sperm per egg by intracytoplasmic sperm injection. Fertilised eggs are cultured for two to six days, usually to the blastocyst stage. One embryo is transferred; the rest are vitrified and stored.

Two changes have reshaped that sequence since the 1990s. ICSI, first reported by a Brussels group in 1992, made severe male-factor infertility treatable and is now used in a majority of cycles worldwide, including many where the indication for it is unclear.[^palermo1992] Vitrification, an ultra-rapid cooling method that avoids ice crystal formation, made frozen embryo and egg storage reliable enough that transferring a thawed embryo in a later cycle is now often preferred to transferring a fresh one. It is the same physical principle that [[cryonics]] proposes to apply to a whole body, working here on a hundred-micrometre object with no vasculature.

## Development history

```timeline
[
  { "year": "1959", "title": "Rabbit IVF confirmed", "text": "Min Chueh Chang produces live rabbit young from eggs fertilised in vitro, establishing that mammalian fertilisation outside the body can yield normal offspring." },
  { "year": "1978", "title": "Louise Brown", "text": "Patrick Steptoe and Robert Edwards report the first human birth after in vitro fertilisation, achieved in an unstimulated cycle with a single egg." },
  { "year": "1990", "title": "Preimplantation testing", "text": "Alan Handyside's group biopsies human embryos and selects by sex to avoid X-linked disease, opening the field of embryo testing." },
  { "year": "1990–1991", "title": "Statutory regulation in the UK", "text": "The Human Fertilisation and Embryology Act creates a licensing authority with a fourteen-day limit on embryo culture, the model most later regimes were measured against." },
  { "year": "1992", "title": "ICSI", "text": "A single sperm injected directly into an egg produces pregnancies, extending treatment to men with almost no motile sperm." },
  { "year": "2010", "title": "Nobel Prize", "text": "Robert Edwards receives the Nobel Prize in Physiology or Medicine; Steptoe had died in 1988 and the prize is not awarded posthumously." },
  { "year": "2012", "title": "Egg freezing leaves the experimental category", "text": "Vitrification results are judged good enough for the American Society for Reproductive Medicine to drop the experimental label from oocyte cryopreservation, and elective egg banking becomes a commercial market." }
]
```

## What it delivers

The dominant variable is the age of the egg, and success rates fall steeply through the late thirties and forties. They are also better described per patient across several cycles than per transfer, and a cumulative live-birth rate is the figure a well-run clinic will quote.

Volume is now substantial. An analysis of four decades of international registry data put the number of children born after assisted reproduction between 1978 and 2018 at between roughly 9.8 and 13 million, with several million more since.[^adamson2025] UK licensed clinics ran more than 77,500 IVF cycles for 52,400 patients in 2023, producing almost 21,000 babies, about one UK birth in thirty-two; the multiple birth rate fell to 3.4% as single embryo transfer became standard.[^hfea2023] That last number is an underrated public-health result, because twin pregnancies carry much of the obstetric risk historically attributed to IVF itself.

> [!key] Why this article sits in the middle of the reproduction portal
> Every embryo technology covered here operates on an embryo outside a body. [[polygenic-embryo-screening]] ranks embryos, [[mitochondrial-replacement-therapy]] rebuilds one, heritable editing would rewrite one, and [[in-vitro-gametogenesis]] would supply the eggs to make far more of them. None of those has an independent route to a pregnancy. IVF is the delivery mechanism for all of them, which is why its cost, its regulation, and the number of embryos a cycle yields set the practical limits on each.

## The platform other technologies stand on

Embryo biopsy and testing are the clearest case. Preimplantation genetic testing for monogenic disease is reliable and uncontroversial where a couple carries a known variant. Testing for aneuploidy is performed on a large share of cycles in some markets, and randomised trials have not shown that it raises live-birth rates per patient.[^munne2019] Polygenic screening extends the same biopsy to complex traits and is rejected as unvalidated by professional genetics bodies.

Beyond selection, IVF is the necessary substrate for anything that edits or reconstructs an embryo. The [[he-jiankui-affair]] was carried out inside ordinary IVF cycles with ordinary equipment, using [[crispr-cas9]] reagents that can be ordered, which is the fact that makes [[governance-of-genome-editing|governance]] hard: the specialised part of heritable editing is a reagent, and the rest is a clinic that exists in most countries. In vitro gametogenesis, if it works in humans, would remove the binding constraint on embryo number and change what [[designer-babies|selection]] could deliver. Spare and donated embryos are also the starting material for human embryonic stem cell lines and for much of what is known about early human development, which is part of why [[induced-pluripotent-stem-cells|induced pluripotent stem cells]] and [[synthetic-embryos|embryo models]] were pursued at all: each reduces the dependence on donated embryos without removing it.

## Add-ons and the evidence problem

IVF is largely a private market even in countries with public health systems, and it sells optional extras: endometrial scratching, immunological treatments, time-lapse incubation, assisted hatching. The UK regulator rates these on a published scale and, at its 2023 overhaul, placed none of the thirteen it had reviewed in the category reserved for treatments shown by multiple good trials to improve live-birth rates.[^hfeaaddons] The scale itself has been criticised for compressing very different kinds of uncertainty into one colour, but the finding is not seriously disputed: patients pay for interventions that mostly have not been shown to work.

> [!caution] What the success rate does not tell you
> A clinic's headline rate depends on which patients it accepts and how it counts. Rates per embryo transferred exclude cycles cancelled before transfer; rates per cycle started include them. Neither figure describes an individual's chance, which is dominated by age and by cause of infertility.

## Risks and outcomes for children

The ovarian stimulation itself carries a small risk of ovarian hyperstimulation syndrome, which has become less common with milder protocols and freeze-all strategies. Egg collection is a minor surgical procedure with the usual bleeding and infection risks.

For the children, the honest summary is that risks are real, small, and hard to attribute. A systematic review and meta-analysis found birth defects modestly more common after assisted reproduction than after natural conception.[^hansen2013] Preterm birth and low birthweight are likewise somewhat more frequent. Whether that is caused by the laboratory procedures, by the underlying subfertility of the parents, or by the multiple pregnancies that were common in earlier practice has never been fully separated, and the same ambiguity attaches to the slightly raised rate of imprinting disorders. Follow-up now extends to adults in their forties without a signal that would change clinical practice.

## Access, law and cost

Regulation ranges from statute to nothing. The United Kingdom licenses clinics and specifies what may be tested for; several European states restrict embryo creation and storage tightly; the United States regulates laboratories and advertising but leaves the substance of practice to professional guidance. The gaps between these regimes drive reproductive travel, and they are the same gaps analysed under [[access-and-inequality]]. Where the law does bind, it binds oddly: the fourteen-day limit on embryo culture written into the UK statute in 1990 was set at a point nobody could then reach, and it is now the constraint the work described under [[ectogenesis]] and embryo modelling runs into.

Funding is where the difference bites hardest. In the UK the NHS-funded share of cycles fell from 35% in 2019 to 27% in 2023, with wide regional variation.[^hfea2023] Elsewhere, cost is the binding constraint on who has children this way, and it compounds every downstream capability: a technology priced as an add-on to a self-funded cycle is available to the population that can already afford the cycle.

Legal status of the embryo is unsettled in a way that can disrupt practice overnight. In February 2024 the Supreme Court of Alabama held that frozen embryos are children under the state's wrongful-death statute; several clinics suspended treatment, and the legislature passed immunity legislation within three weeks.[^lepage2024] The episode is the clearest recent demonstration that IVF's stability rests on a legal settlement about embryo status that is neither uniform nor secure, and that every technology built on top of it inherits that exposure.

## See also

- [[embryo-selection]]
- [[polygenic-embryo-screening]]
- [[in-vitro-gametogenesis]]
- [[mitochondrial-replacement-therapy]]
- [[germline-editing]]
- [[reproductive-longevity]]
- [[artificial-womb]]
- [[uterus-transplantation]]

## References

[^palermo1992]: `paper` Palermo, G., Joris, H., Devroey, P. and Van Steirteghem, A. C. "Pregnancies after intracytoplasmic injection of single spermatozoon into an oocyte." *The Lancet*, 1992. {Four pregnancies from eight treatment cycles in couples for whom conventional insemination had already failed.}
[^hfea2023]: `report` Human Fertilisation and Embryology Authority. *Fertility treatment 2023: trends and figures*. HFEA, June 2025. {UK licensed clinics only; the regulator collects every cycle by statute, which makes the denominator unusually complete.}
[^adamson2025]: `paper` Adamson, G. D., Creighton, P., de Mouzon, J., Zegers-Hochschild, F., Dyer, S. and Chambers, G. M. "How many infants have been born with the help of assisted reproductive technology?" *Fertility and Sterility*, 2025. {A range rather than a count, because national registries differ in coverage and several large markets report incompletely.}
[^munne2019]: `paper` Munné, S. et al. "Preimplantation genetic testing for aneuploidy versus morphology as selection criteria for single frozen-thawed embryo transfer in good-prognosis patients: a multicenter randomized clinical trial." *Fertility and Sterility*, 2019.
[^hfeaaddons]: `regulator` Human Fertilisation and Embryology Authority. "UK fertility regulator launches improved ratings for fertility treatment add-ons." HFEA, October 2023. {A regulator's own rating scheme; the ratings summarise published trial evidence rather than adding new data.}
[^hansen2013]: `paper` Hansen, M., Kurinczuk, J. J., Milne, E., de Klerk, N. and Bower, C. "Assisted reproductive technology and birth defects: a systematic review and meta-analysis." *Human Reproduction Update*, 2013. {Pools observational studies, so it cannot separate the effect of the procedures from that of the parents' underlying subfertility.}
[^lepage2024]: `law` LePage v. Center for Reproductive Medicine, P.C., Supreme Court of Alabama, February 2024. {A wrongful-death ruling about embryos destroyed in a storage accident; it did not restrict IVF directly, and the legislature responded with an immunity statute.}