THE ROLE OF OOCYTE MORPHOLOGY ON FERTILIZATION AND EMBRYO FORMATION IN ASSISTED REPRODUCTIVE TECHNIQUES

Abstract

Objective: To assess the influence of MII oocyte morphology on the
\nfertilization outcome and embryo development in ART cycles. Since, age
\nmay affect the quality of oocyte, the role of women's age was also
\nevaluated following IVF or ICSI cycles. Materials and Methods:200 MII
\noocytes from 30 IVF and ICSI cycles were evaluated. The morphology of
\noocytes that were fertilized in IVF cycles (IVF+) was compared with
\nfailed fertilization (IVF-). The oocytes were similarly categorized in
\nthe ICSI procedure (ICSI+ and ICSI-). The criteria for morphological
\nevaluations were: a. normal oocytes showed clear cytoplasm with
\nhomogenous fine granularity; b. granular oocytes, dark with granularity
\neither homogenous in whole cytoplasm or concentrated in the central
\nportion of the oocyte; c. cytoplasmic inclusions comprised vacuoles
\npresumed to be of endocytotic origin; d. dark zona pellucida (ZP), e.
\nfragmented polar body (PB) of different sizes; f. non-spherical shape
\nof oocyte; and g. wide previtelline space (PVS). Embryo transfer took
\nplace 48 h after insemination/ injection. The statistical significance
\nof the data was analyzed using chi-square and Fisher's exact tests.
\nResults: A total of 67 and 78 oocytes were fertilized in IVF and ICSI
\ncycles, respectively. 46.3% and 35.9% of fertilized oocytes were shown
\nwith normal morphology in IVF and ICSI cases, respectively. The rates
\nof grade A & B embryos were significantly higher in oocytes with
\nnormal morphology (P<0.05). The mean number of embryos transferred
\nwas similar in IVF and ICSI groups (3.3±0.4 versus 3.0±0.9).
\nIn IVF+ and ICSI+, fragmented PBs were the highest rates of single
\nabnormality with 11.9% and 14.1%, respectively. Also, multiple
\nabnormalities were observed in 21.0% and 48.5% of oocytes in IVF+ and
\nIVF-, respectively (P<0.001). 15.4% and 31.8% of the oocytes from
\nICSI+ and ICSI- were presented with more than one abnormality.
\nRefractile bodies were the highest type of single abnormality (18.2%)
\nin ICSI- group. Conclusions: In both IVF and ICSI, the highest rates of
\nfertilization and embryo formation took place in oocytes with normal
\nmorphological features that were retrieved from young patients. The
\nmost single morphological features involved in failed fertilization
\nwere refractile body in ICSI and ooplasm granulation in IVF cases. The
\ndata suggest that oocyte quality plays a major role in fertilization
\nprocess and embryo development in ART program.