Artificial Oocyte Activation (AOA).

What is AOA?

When a sperm meets an egg, it triggers a process called ‘egg activation’ which starts off the process of embryo development, while at the same time allowing only one sperm to fertilise the egg. If the egg doesn’t activate, then it won’t develop.

Egg (or oocyte) activation may be stimulated by chemicals called calcium ionophores. These chemicals can be added to the embryo in the lab.

Risks of AOA

In theory, egg activation using calcium ionophores could cause embryos to have abnormal numbers of chromosomes, which would cause the pregnancy to miscarry. Currently, there’s not enough evidence to decide whether these risks are a serious concern.


Four randomised studies have been undertaken to evaluate the effects of AOA. Three have shown no difference in fertilisation, division and pregnancy rates. A fourth more recent study showed an increased activation for two different compounds but there were concerns regarding the study set-up.

Studies included in this literature review generally report that oocyte activation using calcium ionophore may be effective for selected patients with previous ICSI failures. There is some observational evidence to suggest an increase in fertilisation rates. Only one study involved follow up of children in later years where the children were found to display normal neurodevelopment. More follow up studies should be done to further understanding on whether calcium ionophore is safe to use.

Current HFEA grading

For more information, please visit the HFEA website

Your next step.

When you are ready and the time is right for you, the next step is to contact us and we will help you arrange a face-to-face, telephone or video-call introduction with one of our consultants.

You can do this by filling in the contact form below or by giving one of our friendly team a call on +44 (0) 203 263 6025 or emailing us at