Intracytoplasmic sperm injection: position of the polar body affects pregnancy rate

A prospective study on intracytoplasmic sperm injection (ICSI) was performed to evaluate the effect of the position of the polar body relative to the opening of the injection needle during sperm injection, and of the person who performs the injections on fertilization, cleavage, and pregnancy rates. This study included 173 couples undergoing 313 ICSI cycles from September 1995 to December 1997. All injections were performed by two persons. For each injected oocyte the person who performed the injection was recorded as well as the position of the polar body during injection (6 o'clock: animal pole towards the opening of the needle; 12 o'clock: animal pole away from the opening of the needle). Of 2630 oocytes retrieved, 2232 were injected. Significantly more oocytes developed two pronuclei after injection with the polar body at 6 o'clock versus 12 o'clock (P = 0.01; 51 versus 45% respectively) and after injection by person 1 versus person 2 (P = 0.02; 50 and 45% respectively). Higher pregnancy rate (P = 0.046) was found after transfer of embryos from oocytes injected with the polar body at 6 o'clock (36%) versus 12 o'clock (18%). This was the result of a significant interaction (P = 0.03) between the position of the polar body and the person performing the injections. Given the higher fertilization rate in the 6 o'clock group, it is recommended that oocytes be injected with the polar body at 6 o'clock. The higher pregnancy rate as a result of polar body position and the interaction between polar body position and the operator suggest variations in injection technique.