Abnormal fertilization

A proportion of the inseminated oocytes after IVF or ICSI either do not form pronuclei, or form only I pronucleus (1PN) or multiple pronuclei (3PN, 4PN). After conventional IVF, the presence of multiple PNs means that the oocyte was fertilized by more than just one spermatozoa. These embryos are called polyspermic and have surplus numbers of chromosomes. Polyspermic embryos should not be transferred as they are related in abnormal pregnancies (miscarriages, myli pregnancy).