Methods : In 125 cycles with six or more oocytes retrieved per cycle, sibling oocytes were randomly allocated to IVF or ICSI (group A). In 74 cycles with less than six oocytes retrieved per cycle, cycles were allocated to IVF or ICSI (group B).

Results : In group A, ICSI fertilization rate of 61% per allocated oocyte was higher than IVF fertilization rate of 51.6% (P < 0.001).="" complete="" fertilization="" failure="" occurred="" in="" 19.2="" and="" 0.8%="" of="" cycles="" in="" ivf="" and="" icsi,="" respectively="">P < 0.001).="" in="" group="" b,="" fertilization="" rate="" in="" ivf="" cycles="" was="" 53.3%="" as="" compared="" to="" 60.7%="" per="" allocated="" oocyte="" in="" the="" icsi="" cycles="">P = 0.29). Complete fertilization failure was higher (P = 0.02) in conventional IVF (34.3%) than ICSI cycles (10.3%).

Conclusions : Allocation of sibling oocytes to IVF and ICSI in the first cycle minimizes risk of fertilization failure. For patients with limited number of oocytes, ICSI technique is recommended.