Question
What is In Vitro Fertilization (IVF)? Explain the step-by-step procedure. Why is it called the “test tube baby” technique?
Solution — Step by Step
In Vitro Fertilization (IVF) is an Assisted Reproductive Technology (ART) in which fertilization of an egg and sperm occurs outside the body (in vitro = “in glass”), in a laboratory setting.
It is used when:
- Fallopian tubes are blocked, damaged, or absent (egg cannot travel to uterus)
- Male infertility (low sperm count, poor motility)
- Unexplained infertility after other treatments fail
- To screen embryos for genetic disorders (Preimplantation Genetic Testing)
The term “test tube baby” is a misnomer — fertilization actually occurs in a small glass/plastic dish (Petri dish), not a test tube. The term was popularized after Louise Brown, the world’s first IVF baby, was born in 1978.
Normally, one egg matures per menstrual cycle. In IVF, the woman is given gonadotropin hormones (FSH and LH analogues) via daily injections to stimulate the ovaries to produce multiple mature follicles simultaneously.
The woman’s progress is monitored through blood tests (oestrogen levels) and transvaginal ultrasound.
When follicles reach the right size, an hCG trigger injection is given to complete egg maturation. About 36 hours later, eggs are retrieved.
Under ultrasound guidance and mild anaesthesia, a needle is passed through the vaginal wall into each follicle, and eggs are aspirated. Typically 8-15 eggs are collected.
The eggs are examined in the lab under a microscope and graded by maturity.
Mature eggs are combined with prepared sperm (washed to remove seminal fluid and select the most motile) in a culture dish — this is the “in vitro fertilization” step.
In standard IVF: approximately 50,000-100,000 sperm are placed with each egg.
In severe male infertility: ICSI (Intracytoplasmic Sperm Injection) is used — a single sperm is injected directly into the egg using a micro-needle.
Fertilization is confirmed 16-18 hours later by checking for two pronuclei (one from egg, one from sperm).
Fertilized eggs develop in the incubator for 3-5 days.
- Day 3: Cleavage stage embryo (6-8 cells)
- Day 5: Blastocyst stage (more differentiated, ~100 cells)
Blastocyst transfer has higher success rates.
Embryos are graded by morphology. The best quality embryo(s) are selected for transfer. Surplus embryos can be frozen (cryopreservation) for future cycles.
One or two embryos are loaded into a thin catheter and gently placed into the uterine cavity through the cervix. This is typically painless.
After the transfer, the woman takes progesterone supplements to support the uterine lining.
A pregnancy test (blood hCG) is done 14 days later.
Why This Works
IVF bypasses the fallopian tube entirely — eggs go directly from ovary to lab to uterus. This is why it works for tubal blockage. The laboratory conditions (precise temperature, CO₂ levels, culture media) mimic the environment of the fallopian tube.
Success rates depend on age: 35-40% per cycle for women under 35, declining to ~5% for women over 42.
Common Mistake
Students write that in IVF, development of the baby occurs in the test tube/lab. Wrong — only fertilization and early embryo development (for 3-5 days) occur in the lab. The embryo is then transferred to the mother’s uterus, where it implants and the rest of pregnancy proceeds normally. The baby is born naturally — only the fertilization step was done “in glass.”