In vitro fertilization and human embryo transfer: biological problems

Optimal results in in-vitro fertilisation procedures can only be achieved using both meiotic competent, mature oocytes and spermatozoa with a high fertilization potential. This situation is not verified in the overwhelming number of couples submitting to IVF-ET. Many of the steps in the gametes maturation processes need to be urgently clarified in order to reach optimal fertilization rates.