THE INFLUENCE OF THE SITE OF SPERM DEPOSITION AND MODE OF OOLEMMA BREAKAGE AT INTRACYTOPLASMIC SPERM INJECTION ON FERTILIZATION AND EMBRYO DEVELOPMENT RATES

The aims of this study were to examine, in a prospective, controlled w ay, the effect of the sperm deposition site in the oocyte and the mode of oolemma breakage in intracytoplasmic sperm injection (ICSI) on fer tilization and embryo development rates. In the first trial (100 cycle s in total), the spermatozoa were deposited further from the meiotic s pindle (polar body at the 12 o'clock position) in half of the oocytes (n = 649), while in the other half (n = 605) the spermatozoa were depo sited nearer to the meiotic spindle (polar body at the 6 o'clock posit ion). In the second trial (6860 oocytes in 624 cycles), five different modes of membrane breakage (the reaction of the oolemma to the penetr ating injection needle) at the moment of injection were noted: oolemma breakage, type A pricking once, no suction (n = 1401); type B, pricki ng once, small suction (n = 2761); type C, pricking once, long suction (n = 2310); type D, pricking twice or more, no or small amount of suc tion (n = 259); and type E, pricking twice or more, long suction (n = 129). No differences were observed between the 12 and 6 o'clock positi ons in the survival rate (90 and 90% respectively) and in the normal f ertilization rates (78 and 77% respectively). Significantly more trans fer quality embryos (less than or equal to 50% fragmentation) were obt ained in the 6 o'clock position group (83%) than in the 12 o'clock pos ition group (79%). In the second trial, significantly lower survival r ates were noted after membrane breakage type A (82%) than after breaka ges of types B, C, D and E (93, 92, 88 and 88% respectively). There we re no significant differences present in the normal fertilization rate s (70, 72, 70, 71 and 73% for types A-E respectively), but significant ly more freeze quality embryos (less than or equal to 20% fragmentatio n) were obtained after injection B (65%) than after injection types A, C, D and E (59, 61, 55 and 51% respectively). In conclusion, the site of sperm deposition in the oocyte does not influence the normal ferti lization rate but does affect the embryo development rate. Furthermore , the mode of membrane breakage does not influence the normal fertiliz ation rate but does affect oocyte survival and embryo development rate s.