In 1978, Louise Brown was born in Oldham, England — the first person in history conceived outside a mother's body. Her arrival sparked waves of ethical debate and newspaper headlines about 'test-tube babies'. Today, nearly fifty years later, more than eight million people owe their existence to in vitro fertilisation. IVF has become a routine medical procedure — the most widely used and extensively studied in reproductive medicine.
Yet the word 'IVF' still tends to provoke a mixture of hope, anxiety and confusion. What exactly happens? How complicated is it? Is it painful? What are the chances? This article answers those questions — without over-simplifying, and without unnecessary jargon.
In vitro fertilisation is the process by which eggs are retrieved from the ovaries, fertilised with sperm in a laboratory, and the resulting embryo transferred into the uterus. 'In vitro' means literally 'in glass' — this is where fertilisation takes place, which in natural conception happens inside the fallopian tube. Everything that follows — pregnancy, birth, the child — is no different from usual.
A key point: IVF does not alter genetics. A child born through IVF using a couple's own eggs and sperm is genetically identical to one conceived naturally. The location of fertilisation has no effect on DNA.
In a natural cycle, the ovaries produce one mature egg per month. IVF requires more — because not every egg will fertilise, not every fertilised embryo will survive to transfer, and not every transfer will result in pregnancy. The more good-quality eggs retrieved, the better the overall odds.
To achieve this, daily injections of gonadotrophins — hormones that stimulate multiple follicles to mature simultaneously — are given over 10 to 14 days. This is neither dangerous nor 'uses up' the egg supply: in each natural cycle the body selects one follicle from a pool that already exists; the rest are lost. Stimulation simply rescues these follicles from natural attrition.
Monitoring ultrasounds are carried out throughout stimulation, tracking follicle growth. When follicles reach the right size — around 18 to 20 mm in diameter — a 'trigger' injection is given to initiate final egg maturation. Exactly 36 hours later, egg retrieval takes place.
Side effects of stimulation: bloating, a sense of heaviness in the ovaries, mood changes. The main serious complication — ovarian hyperstimulation syndrome (OHSS) — occurs in around 1–2% of cycles with modern mild protocols. Severe forms are rare.
Egg retrieval is a minimally invasive procedure performed under sedation or light general anaesthesia — rarely under local anaesthetic. The doctor passes a thin needle through the vaginal wall under ultrasound guidance and aspirates the fluid from each follicle. The whole procedure takes 15 to 30 minutes.
The follicular fluid is immediately passed to the embryologist, who examines it under a microscope to locate the eggs. The typical yield is 8 to 15 eggs with standard stimulation, though this varies considerably depending on age and ovarian reserve.
After retrieval: a few hours of observation and rest. Most patients go home the same day. Mild abdominal discomfort for a day or two is normal.
Mature eggs are fertilised by one of two methods. Conventional IVF: the egg is placed in a dish with sperm and one spermatozoon penetrates on its own. ICSI (intracytoplasmic sperm injection): the embryologist manually injects a single sperm directly into the egg using a microscopic needle. ICSI is used when there is a male factor — low sperm count or motility.
The next morning, fertilisation is checked. A normal result shows 'two pronuclei' — confirmation that the egg and sperm DNA have united. The embryos continue to develop in an incubator under precisely controlled conditions of temperature, humidity and gas composition.
A curious fact: the culture medium for growing embryos is one of the most closely guarded trade secrets in reproductive medicine. Leading clinics develop and patent their own formulations, designed to mimic the environment of the fallopian tube.
Embryos are cultured for three to five days. By day five they reach the blastocyst stage — a hollow sphere of around 100 cells divided into two populations: the inner cell mass (which will become the baby) and the trophoblast (the future placenta). Transfer at the blastocyst stage is generally preferable to day-three transfer, as it allows selection of embryos that have passed a key biological checkpoint.
Embryos are assessed by morphological criteria: shape, size, rate of division, degree of fragmentation. This is an imperfect but informative assessment. A more precise method is preimplantation genetic testing (PGT): a biopsy of a few cells followed by chromosomal analysis. PGT identifies embryos without chromosomal abnormalities — the leading cause of failed transfers and miscarriage.
Transfer is the simplest stage technically and the most emotionally charged. A thin catheter is passed through the cervix and the embryo is deposited into the uterine cavity. The procedure takes a few minutes, is virtually painless, and requires no anaesthesia. Many patients describe it as similar to a smear test.
Typically, one embryo is transferred. This reduces the risk of multiple pregnancy, which carries considerably higher risks for both mother and children than a singleton. The idea that transferring more embryos gives better odds is a myth: with modern laboratory standards, single embryo transfer delivers comparable success rates with far lower risk.
After transfer, progesterone support is prescribed — a hormone that prepares the endometrium for implantation and sustains early pregnancy. A blood test for hCG follows 10 to 14 days later.
The question 'what are the chances with IVF' has no single answer — because the main factor is the woman's age, or more precisely, the age of her eggs. Approximate figures from European registries: under 35 — around 40–45% live births per transfer; 35–37 — 30–35%; 38–40 — 20–25%; over 40 with own eggs — 10% and below.
With donor eggs, success rates are considerably higher and much less age-dependent for the recipient — because what matters is the donor's age. This is one of the strongest arguments for donor IVF when ovarian reserve is low or after 40.
Important: 40% per transfer does not mean 40% per cycle. If several embryos were produced in a cycle, each one represents a separate chance. The cumulative likelihood of a live birth across a full IVF cycle — including all frozen embryos — is significantly higher than the odds of a single transfer.
'IVF children are less healthy' — false. Large-scale long-term studies have found no meaningful difference in health outcomes between IVF-conceived children and those conceived naturally. Small increases in certain birth anomalies observed in early research are largely attributable to parental characteristics — age, underlying infertility — rather than the procedure itself.
'IVF uses up the egg supply' — false. As explained above, stimulation recruits follicles that would have been lost in that cycle anyway. A woman is not reproductively 'older' after IVF than before it.
'IVF is a last resort' — false. IVF is one tool in reproductive medicine, and in some situations it is the appropriate first-line treatment, not a fallback when everything else has failed. A fertility specialist recommends IVF when it is the most clinically effective option for a given situation — not as a last roll of the dice.
'IVF always works first time' — also false. A first transfer results in pregnancy in roughly a third of cases in younger patients, and considerably less often after 38. Multiple attempts are not the exception — they are the statistical norm.
IVF is indicated for: blocked fallopian tubes (sperm physically cannot reach the egg); severe male factor infertility (especially with ICSI); significant endometriosis; unexplained infertility after several unsuccessful attempts with less invasive methods; reduced ovarian reserve when time is a critical factor; the need for preimplantation genetic testing.
IVF is also the method of choice for people planning a family without an opposite-sex partner: single women, lesbian couples (including reciprocal IVF), and male same-sex couples in countries where surrogacy is available.
IVF is not magic, and it is not a guarantee. It is a medical procedure with a well-understood mechanism, known risks, and statistically measurable odds. In nearly fifty years of existence it has helped more than eight million people come into the world — and it continues to improve.
If you have just found out about IVF — whether because you are experiencing difficulty conceiving, or because you are planning a family and exploring your options — the most useful next step is a consultation with a fertility specialist who can assess your individual situation. Statistics matter, but decisions are always made for a specific person, not for a table average.
Blastocyst — the stage of embryo development reached on days 5–6 after fertilisation: a hollow sphere of ~100 cells, optimal for transfer or freezing.
FET (frozen embryo transfer) — transfer of a previously frozen and thawed embryo into a prepared endometrium.
Gonadotrophins — hormonal preparations (FSH and LH or analogues) used to stimulate the growth of multiple follicles in one cycle.
hCG (human chorionic gonadotropin) — the hormone produced after embryo implantation. Its presence in the blood confirms pregnancy.
ICSI (intracytoplasmic sperm injection) — a fertilisation method in which a single sperm is injected directly into an egg using a microscopic needle.
OHSS (ovarian hyperstimulation syndrome) — a complication of stimulation in which the ovaries react excessively to hormone treatment. Severe forms are rare with modern protocols.
Ovarian reserve — the remaining egg supply in the ovaries, assessed by AMH level and antral follicle count on ultrasound.
PGT (preimplantation genetic testing) — biopsy of embryo cells and chromosomal analysis before transfer, allowing selection of chromosomally normal embryos.
Trigger injection — an injection (usually hCG or a GnRH agonist) that initiates final egg maturation. Retrieval takes place exactly 36 hours later.
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