Orientation of the first polar body of the oocyte at 6 or 12 o'clock during ICSI does not affect clinical outcome.

This study was designed to clarify whether orientation of the first polar body (PB) of the oocyte at 6 o'clock rather than 12 o'clock, during intracytoplasmic sperm injection (ICSI), significantly affects a number of clinically important outcome measures including fertilization, zygote cleavage, embryonic morphology, and clinical pregnancy and implantation rates. In all, 114 patients were allocated to one of two groups on the basis of strict alternation, both groups being treated by the same ICSI practitioner. In one group, all oocytes were injected with their first PB at 6 o'clock, whereas in the other, the orientation of the PB was reversed (12 o'clock). In all cases, a normally bevelled injection pipette was inserted into the oocyte in the 3 towards 9 o'clock direction. The orientation of the PB did not significantly affect the proportion of oocytes that failed to survive injection or the proportion scored as having either zero, one, two or three pronuclei. The proportion of normally fertilized zygotes that cleaved was not significantly different between the two groups, nor was the proportion of embryos classified as either grade 1, 2 or 3. However, the proportion of grade 4 embryos (the poorest grade) was significantly lower in the 12 o'clock, compared to the 6 o'clock group. Most importantly, there was no significant difference between the two groups in the proportion of patients having a positive clinical pregnancy test, nor in either the implantation rate or the mean number of fetal hearts detected per patient presenting with a clinical pregnancy.