# ICSI

> Citation bundle for ICSI on The Treatment Registry.
> URL: https://thetreatmentregistry.com/procedures/icsi
> Bundle URL: https://thetreatmentregistry.com/api/citations/procedures/icsi

- Category: ivf-fertility

## Description

Intracytoplasmic sperm injection is an in vitro fertilization (IVF) procedure in which a single sperm cell is injected directly into the cytoplasm of an egg. This technique is used in order to prepare the gametes for the obtention of embryos that may be transferred to a maternal uterus.

## Overview

Intracytoplasmic sperm injection (ICSI) is an in-vitro fertilisation (IVF) procedure in which a single sperm cell is injected directly into the cytoplasm of an egg. Because the sperm is placed inside the egg, the acrosome reaction that normally allows a sperm to penetrate the egg is bypassed; as a result ICSI needs only one sperm cell per oocyte, compared with the 50,000 to 100,000 required for conventional IVF. The steps before and after insemination are otherwise the same, and once fertilised the egg develops into a pre-embryo that is transferred to the uterus to continue developing. ICSI is used most commonly to overcome male infertility, but it may also be used when eggs cannot easily be penetrated by sperm, in cases of abnormal sperm shape (teratozoospermia), in azoospermia — where no sperm are ejaculated but some can be recovered from the testis — with sperm preserved before chemotherapy, or after previous unsuccessful IVF cycles, and occasionally alongside sperm donation. The procedure follows transvaginal retrieval of one or more eggs. A sperm sample is provided on the same day; if none is present, sperm may be recovered from the epididymis (percutaneous epididymal sperm aspiration, PESA) or the testicle (testicular sperm aspiration, TESA). Under a microscope, micromanipulation tools hold the mature egg while a fine glass micropipette collects a single, immobilised sperm, pierces the egg's outer membrane and releases the sperm inside. The first human pregnancy generated by ICSI was achieved in 1991 by Gianpiero Palermo and his team.

## Common risks

- Contradictory evidence on a possible increase in birth defects
- Possible transmission of selected genetic abnormalities to offspring
- Possible vertical transmission of hepatitis B, where evidence is insufficient

## FAQs

### Why IVF (in vitro fertilisation) is done?

IVF (in vitro fertilisation) is a type of [fertility treatment](https://www.nhs.uk/conditions/infertility/).

### How well it works?

Your chance of having a baby using IVF can depend on many factors such as:

### What happens during IVF (in vitro fertilisation)?

A full cycle of IVF (in vitro fertilisation) takes around 3 to 6 weeks to complete. It usually follows 6 steps, depending on the type of treatment you’re having.

### What is ICSI?

Intracytoplasmic sperm injection is an in-vitro fertilisation procedure in which a single sperm cell is injected directly into the cytoplasm of an egg. This prepares the gametes to obtain embryos that may then be transferred to the uterus.

### How does ICSI differ from conventional IVF?

The main difference is at insemination: ICSI needs only one sperm cell per egg, while conventional IVF needs 50,000 to 100,000, because in IVF the acrosome reaction must take place and thousands of sperm are involved. With ICSI the acrosome reaction is skipped, but the steps before and after insemination are the same.

### When is ICSI used?

It is most commonly used to overcome male infertility. It may also be used when eggs cannot easily be penetrated by sperm, in teratozoospermia (abnormal sperm shape), in azoospermia where sperm can be recovered from the testis, with sperm preserved before chemotherapy, after previous unsuccessful IVF cycles, and occasionally alongside sperm donation.

### What happens if there is no sperm in the sample?

If the sample contains no sperm, sperm may be extracted surgically, either from the epididymis, known as percutaneous epididymal sperm aspiration (PESA), or from the testicle, known as testicular sperm aspiration (TESA).

### Is ICSI safe?

The Practice Committee of the American Society for Reproductive Medicine considers ICSI a safe and effective therapy for male-factor infertility, but notes it may carry an increased risk of transmitting selected genetic abnormalities to offspring. Studies on whether birth defects are increased have shown contradictory results.

## Alternative treatments

- **Conventional IVF** — Appropriate when sperm parameters are adequate; lower fertilisation manipulation.
- **Donor sperm IVF** — When severe male-factor cannot be overcome by ICSI; ethical/relational considerations.

## Sources

- [ESHRE — Clinical Practice Guidelines (ART, infertility, ICSI, donor cycles)](https://www.eshre.eu/Guidelines-and-Legal/Guidelines) — European Society of Human Reproduction and Embryology (accessed 2026-06-29)