Every sperm is different. Some are not fully developed, some are deformed and some are too slow to reach the ovum. But even the fastest, completely normal-looking sperm sometimes carry defective genetic material. In nature, these sperm usually cannot bind to the ovum and therefore cannot fertilise it. Sperm that include intact genetic material can, however, usually bind to the hyaluronic acid in the shell of the ovum and then fertilise the ovum.
Fertilisation through ICSI
In fertilisation of the ovum through ICSI this natural “safety mechanism” is bypassed. As long as the sperm looks good and can swim well, it is injected into the ovum. The selection of sperm, takes place here only on the basis of appearance and the swimming characteristics of the sperm.
This is unproblematic because the chance of getting a sperm with defective genetic material is very low in most men.
In some couples, who have repeatedly low fertilisation rates or other failures during ICSI treatments, it can, however, be the case that an above average number of sperm are “defective” and that these cannot fertilise the ovum.
In physiological ICSI (PICSI) the sperm are placed onto a laboratory dish that is coated with hyaluronic acid. Only those sperm that bind to the hyaluronic acid are used for an injection into the ovum.
Studies have shown that PICSI increases the certainty of using a sperm with intact genetic material by about a factor of four (Parmegiani et al. 2010).
PICSI treatment is recommended in the case of:
- Low fertilisation rates in previous ICSI treatments
- Failure to implant
- Delayed development of embryos
- Repeated miscarriages
The additional costs for PICSI treatment are not covered by the health insurance companies.