Before it can attach itself to the uterine lining, the embryo must ‘hatch’ – quite literally, it must break out of a protective shell called the zona pellucida. However, for some embryos (like for patients who are older or who have had repeated IVF failures) it is thought that this might not be happening – even if the embryo reaches the right place, it can’t stay there.

Assisted hatching attempts to combat this using a laser to make a small hole in the embryo shell. Currently, this technique is categorised as “red” on the HFEA’s traffic light rating system in view of insufficient evidence showing improvement in pregnancy rates and is therefore not recommended for routine use.