Optimal polar bodies angle for higher subsequent embryo viability: a pilot study.

OBJECTIVE: To determine the optimal polar bodies (PB) angle for higher subsequent embryo implantation potential.

DESIGN: Prospective study.

SETTING: Academic fertility center.

PATIENT(S): From January to July 2015, 116 patients were recruited in their first IVF-ET cycles.

INTERVENTION(S): At the pronuclear stage, PB angle was measured with the use of E-ruler 1.1.

MAIN OUTCOME MEASURE(S): The primary outcome measure was good-quality embryo rate. Secondary measures were clinical pregnancy rate (CPR) and embryo implantation rate (IR).

RESULT(S): A total of 1,103 oocytes were retrieved. PB angle was measured in 454 zygotes, and 164 of their subsequent embryos were transferred into the uterus. All-or-none implantation took place in 129 embryos, and 89 patients accepted fresh embryo(s) transfer with known PB angle. By means of receiver operating characteristic analysis, the optimal PB angle for subsequent embryo implantation was 24.25°. Based on this cutoff value, 454 zygotes were divided into two groups: small-angle and large-angle. A higher percentage of small-angle zygotes developed into good-quality embryos (70.97% vs. 58.58%). CPR and IR both decreased progressively from purely small-angle embryos to mixed embryos to purely large-angle embryos (CPR: 72.41% vs. 38.46% vs. 26.47%, respectively; IR: 63.27% vs. 26.92% vs. 16.67%, respectively).

CONCLUSION(S): Noninvasive assessment of PB angle is a viable technique for zygote selection and should be included in embryo selection parameters.

CLINICAL TRIAL REGISTRATION NUMBER: ChiCTR-OOC-15005882.