Influence of polarization effects in ooplasma and pronuclei on embryo quality and implantation in an IVF program

The presence of a clear half-moon-like zone of cytoplasm in oocytes is called "halo effect." The prognostic value of this effect is not yet determined. Aligned nucleoli in pronuclei (PN) represent a further polarization phenomenon and a marker for implantation potential. Aim of the prospective study was to evaluate the influence of the halo effect on IVF outcome and to compare the results with observed polarization in PN.

A total of 374 cycles with embryonic transfer were analyzed regarding halo effect and pattern of nucleoli. The oocytes were single-cultured to observe the following embryo quality of each PN stage.

Cycles with halo-positive oocytes showed a significant higher pregnancy rate (44.0% vs. 31.1%; p < 0.05). Furthermore, higher pregnancy rates in cycles with polarized nucleoli were observed. Polarized PN resulted in a significant lower fragmentation and higher cleavage rate of embryos. The fragmentation rate was significantly lower in halo+ oocytes, but the cleavage rate was not influenced.

The results indicate that the presence of a polarized zone of human fertilized oocytes can be a useful indicator for good oocyte quality. Since the origin of ooplasmic polarization seems to be a different process compared with the alignment of nucleoli, the observation will give additional predictive information about the implantation potential.