Oocyte maturation in human in vitro fertilisation programmes.
Oocyte immaturity represents a serious loss of efficiency in the in vitro fertilisation (IVF) treatment cycle since it is associated with a great list of detrimental effects mainly reflected in lower fertilisation and pregnancy rates. In stimulated cycles, oocyte maturation depends on stimulation protocol, ovarian response, time of human chorionic gonadotrophin (hCG) administration, hCG to oocyte retrieval interval, and/or time of in vitro culture period before insemination. The present review discusses the influence of these factors on human oocyte maturation and proposes several preventive and corrective measures. Due to the difficulty of ascertaining the grade of oocyte maturity based on morphological and physical properties of the oocyte-corona-cumulus complex (OCCC), fertilisation rate has been considered as an indirect index of nuclear and cytoplasmic maturation. The proportion of immature oocytes increases as the ovarian response to gonadotrophins increases. However, the detrimental effects of oocyte immaturity in high responders may be balanced by the higher number of oocytes retrieved per patient (and available embryos for transfer) and the selection of the best embryos for transfer. Oocyte immaturity might be prevented by delaying hCG injection and/or oocyte retrieval. Corrective strategies would involve in vitro or in vivo culture before insemination; addition of gonadotrophins or epidermal growth factor to the culture medium; and coculture with granulosa cells.
Tarín
J J
JJ
Instituto Valenciano de Infertilidad, Spain.
Pellicer
A
A
D005260:Female; D005307:Fertilization in Vitro / Q000379:methods*; D006801:Humans; D009866:Oogenesis; D010062:Ovulation Induction