Does the orientation of the first polar body during ICSI affect fertilization and embryo development rates?

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Objective: To evaluate the relationship between injection site relative to polar body orientation during ICSI and resulting fertilization and embryo development rates. Design: Prospective study of patients undergoing ICSI in a private practice IVF clinic. Materials and Methods: Sibling oocytes from 263 patients under the age of 39 undergoing IVF with ICSI were assigned to 2 groups. In Group A, oocytes were injected in the traditional fashion with the first polar body at either the 6 or 12 o’clock position and the insertion of the ICSI needle at 3 o’clock. In Group B, no particular attention was paid to first polar body alignment except the microinjection needle did not intrude the first polar body. Fertilization and oocyte atresia rates were noted 16–19 hours post ICSI. Embryo development was evaluated on transfer day 3. All ICSI were performed by a single operator. Results: See table. a# Oocytes injected2-PN fertilization rate (%)Abnormal fertilization rate (%)Atresia rateap>0.05 no significance.% Embryos 6–8 cell D3ap>0.05 no significance.Group A97477.32.02.968.3Group B88071.72.94.062.0a p>0.05 no significance. Open table in a new tab Conclusion: Traditionally, the first polar body was thought to be closely associated to the meiotic spindle position of metaphase II (MII) oocytes. During ICSI, the first polar body was usually at the 12 or 6 o’clock position with the injection site at the 3 o’clock position to avoid spindle damage. Recent advances in spindle imaging has challenged this conventional theory. Wang et al. found that using the PolScope, the first polar body did not always predict spindle location accurately. The present study indicates that fertilization rate, embryo development rate and incidence of post injection oocyte injury are not significantly affected by an injection site dependent on polar body orientation. As long as spindle integrity is not damaged during the ICSI process, fertilization and embryo development rates are not compromised. We hypothesized that the size of the meiotic spindle is so small that the likelihood of damage during the ICSI process is low. It is noted that although there was no significant differences between Group A and B, there was a trend towards lower fertilization rate, cleavage rate and higher atretic rate with oocytes that were injected with no particular orientation of first polar body.