**16. ICSI after previous ICSI cycle failure**

132 Enhancing Success of Assisted Reproduction

IVM procedure [151].

**15. Oocyte morphology** 

embryos. It should be noted that the immature oocytes collected in stimulated cycles have already been under stimulation with high doses of gonadotropins and are exposed to hCG before retrieval. The nuclear maturation, cytoplasmic maturation and ensuing developmental capacity of these oocytes may very well be different in comparison with immature oocytes collected from small antral follicles of unstimulated ovaries in the typical

Poor oocyte morphology is a major determinant of failed or impaired fertilization. Normal features of a healthy mature oocyte at Metaphase-II (MII) include presence of a polar body, a round even shape, light colour cytoplasm with homogenous granularity, a small perivitelline space without debris and a colourless zona pellucida. In denuded oocytes, it is possible to assess the morphology and the nuclear maturity but not the cytoplasmic maturity. The MII oocytes with apparently normal cytoplasmic organization may exhibit extra-cytoplasmic characteristics, such as increased perivitelline space, perivitelline debris and/or fragmentation of the first polar body, which may reduce developmental competence of the oocyte [152]. It is common that extra-cytoplasmic and cytoplasmic dysmorphism occur together in the same oocyte **(Figure 4 and 5)**. The dysmorphic phenotypes, which arise early in meiotic maturation, may be associated with failed fertilization and aneuploidy, while those occurring

later in maturation may cause a higher incidence of developmental failure [153, 154].

**Figure 4.** Oocytes in both rows show extra-cytoplasmic and cytoplasmic dysmorphism.

Decreased fertilization rates due to some oocyte dysmorphisms have been reported [152], while others failed to observe that association [155, 156, 157, 158, 159]. Lower pregnancy and implantation rates result when the transferred embryos originate from cycles with >50% dysmorphic oocytes and the same dysmorphism repeats from cycle to cycle [155]. The repetitive organelle clustering is associated with an underlying adverse factor affecting the entire follicular cohort. The presence of a dark cytoplasm decreases by 83% the likelihood of obtaining good quality embryos [160]. However, another study did not find any adverse impact of dark colour of the oocytes on fertilization, embryo development and pregnancy Repeated ICSI treatment can be useful or necessary because there is a high possibility of achieving normal fertilization if a reasonable number of oocytes with normal morphology are available and motile sperm can be found. If there are no motile sperm present in the first ejaculate, a second sample should be required followed by PESA or TESE to obtain motile sperm. In this way, a sufficient number of motile sperm for ICSI are usually found in most men with severe asthenozoospermia.

A history of failed fertilization may be related to some gamete abnormality that may be modified or corrected at the next cycle. It has been documented that for a particular patient, fertilization results can be quite varied when followed through several ICSI cycles at the same centre [169]. The differences between fertilization rates are unexplained, although fluctuations in the gamete quality are probably contributory. Pretreatment endocrine assays and semen analyses prove to be of little value in forecasting failed fertilization. One-third of the patients with TFF achieved pregnancy with their own oocytes in a subsequent ICSI cycle [10]. Since follow-up ICSI treatment has been shown to result in fertilization in 85% of cases, repeated ICSI attempts are suggested in TFF [4, 170].

Intracytoplasmic Sperm Injection – Factors Affecting Fertilization 135

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