Submitted by Dr. Hesham Al-Inany, M.D. Lecturer, Gynaecology & Obstetrics dept. Kasr El-Aini hospital, Cairo University, Egypt.
Evaluation of the fertilization process
It is of a great importance to view the oocyte in a pronuclear stage 12-20hs after insemination to determine whether sperm activity has been good and penetration of the oocyte has occurred ( wood & Trounson , 1989).
This can be confirmed by the visualization of the second polar body and the two pronuclei. If multiple pronuclei are present, then the diagnosis of polyspermic fertilization can be made, and should be discarded or used in research (Sathananthan and Trounson, 1985).In rare cases, single pronucleus is visible, this can either be male or female. If other indications of fertilization are present, so it is probably due to delay in formation of the 2nd pronucleus. Additional 24hs of culture will bring the majority of the fertilized eggs into cleavage of two to eight cells.Ron-EL et al, (1991) reported that delayed fertilization can be due to immaturity of the oocytes or impaired sperm quality. If due to immaturity, once fertilization takes place, the chances to achieve embryos with good morphology are almost equal to those observed in oocytes fertilized in time .On the other hand, delayed fertilization due to sperm difficulty in penetrating oocytes usually leads to low fertilization rate, poor embryo morphology and low chances of conceiving.
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