Question
Explain the steps of In Vitro Fertilisation (IVF). How is it different from GIFT, ZIFT, and ICSI?
This question appeared in NEET 2024 and is a standard 3-marker in CBSE Class 12 boards. Reproductive health carries high weightage in NEET Biology — ART questions come almost every year.
Solution — Step by Step
The woman is given hormonal drugs (gonadotropins) to induce superovulation — her ovaries release multiple eggs instead of one.
We do this to collect several oocytes at once, increasing success chances. A single cycle is expensive and physically demanding, so maximising eggs per attempt matters.
Eggs (oocytes) are retrieved from the ovaries via a minor surgical procedure. Sperm is collected from the male partner (or donor) and processed — slow and dead sperms are removed.
The sample is capacitated in the lab, which mimics what normally happens inside the female reproductive tract.
The egg and sperm are placed together in a culture dish under controlled temperature, pH, and nutrition. Fertilisation happens outside the body — this is the “in vitro” part (vitro = glass).
The resulting zygote is allowed to develop into an embryo (2–8 cell stage) in the incubator.
The embryo is transferred into the uterus — this step is called Embryo Transfer (ET) or more precisely Intra Uterine Transfer (IUT).
If the embryo has more than 8 cells, it is transferred to the uterus. If it’s at the zygote stage (just fertilised), it can be placed in the fallopian tube instead — that’s ZIFT.
The embryo implants in the uterine wall and develops normally. The baby born through this process is called a test tube baby — though nothing happens in a test tube; it’s a culture dish.
| Technique | Full Form | What’s Transferred | Where |
|---|---|---|---|
| IVF + ET | In Vitro Fertilisation + Embryo Transfer | Embryo (2–8 cells) | Uterus |
| ZIFT | Zygote Intra Fallopian Transfer | Zygote | Fallopian tube |
| GIFT | Gamete Intra Fallopian Transfer | Eggs + Sperm (unfertilised) | Fallopian tube |
| ICSI | Intra Cytoplasmic Sperm Injection | Sperm injected into egg directly | Lab (then transferred) |
Why This Works
IVF bypasses the two most common infertility causes: blocked fallopian tubes (egg can’t meet sperm) and low sperm count (sperm can’t reach egg). By bringing egg and sperm together in a controlled environment, we sidestep the problem entirely.
GIFT is for couples where the woman’s fallopian tubes are functional — fertilisation still happens inside the body, just at the right location. ZIFT is a middle ground: fertilisation is confirmed in the lab, but the zygote is placed in the tube to travel naturally to the uterus.
ICSI is reserved for severe male infertility — cases where even a few motile sperms are unavailable. A single sperm is literally injected into an egg using a microneedle. It’s the most precise ART technique and has dramatically improved outcomes for male-factor infertility.
Alternative Method: Surrogate Mother
When the woman cannot carry the pregnancy herself (uterine issues, health conditions), a surrogate mother is used. The embryo formed from the biological parents’ gametes is transferred into the surrogate’s uterus.
The child is genetically the biological parents’ — the surrogate only provides the womb. This is legally and ethically regulated in India under the Surrogacy (Regulation) Act, 2021.
NEET often asks: “A woman with blocked fallopian tubes but healthy uterus — which ART is best?” Answer: IVF + ET (embryo transfer to uterus), NOT GIFT or ZIFT (those need functional tubes).
Common Mistake
Students confuse ZIFT and GIFT by mixing up what is transferred.
GIFT = Gametes (egg + sperm, unfertilised) → Fallopian tube
ZIFT = Zygote (fertilised egg) → Fallopian tube
The word itself is the clue — Gamete in GIFT, Zygote in ZIFT. In both, the destination is the fallopian tube, not the uterus. Writing “uterus” for ZIFT in NEET is a classic 1-mark loss.
Also: IVF and ICSI both involve in vitro fertilisation. ICSI is a type of IVF where sperm is injected directly — they are not mutually exclusive techniques.