First principle: match the technology to where the chain is broken
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| Technique | Fertilisation site | Requirement / best fit |
|---|---|---|
| IUI | in vivo (tube) | washed sperm into uterus; needs a patent tube; mild male/cervical/unexplained |
| IVF | in vitro | stimulate → retrieve → fertilise → transfer; bypasses tubes; tubal disease, and broad indications |
| ICSI | in vitro (single sperm injected) | severe male factor, prior fertilisation failure |
The reasoning
- IUI only relocates sperm — tubal function is still required.
- IVF removes the tube from the equation → the answer for tubal‑factor infertility (e.g. post‑PID, hydrosalpinx after treatment).
- ICSI overcomes the sperm–oocyte penetration step → severe male factor.
The complication to respect 🚩
Pitfalls
- Offering IUI when tubes are blocked (it cannot work).
- Ignoring hydrosalpinx before IVF (lowers success).
- Under‑estimating OHSS risk in PCOS.
Pearls
- 🎯 IUI needs a tube; IVF bypasses the tube; ICSI bypasses sperm penetration. Watch OHSS in PCOS.
- 🩺 A woman with bilateral tubal disease should go to IVF — don't waste cycles on IUI.
Next → Back to the start of reproductive life — puberty (Concept 34).