Are there non-invasive markers in human oocytes that can predict pregnancy outcome?

Predictive criteria for selection of the best embryo for single embryo transfer remain elusive. This study aimed to determine if non-invasive markers in human oocytes, detectable using polarized light microscopy, can predict pregnancy outcome. Twenty-two pregnancy-producing oocytes from 19 patients had their morphological features compared with 30 oocytes from 19 age-matched patients whose transfer did not result in a pregnancy. Both pregnant and non-pregnant patients had similar numbers of oocytes collected (average: 11.9 +/- 2.8 versus 11.3 +/- 2.9) and similar fertilization rates (70.1% versus 69.6%). All embryos transferred were 4-cell cleavage-stage on day 2 with <10% fragmentation. Meiotic spindles were examined at 39-40 h following human chorionic gonadotrophin administration for spindle normality, length, density and angle from first polar body. There was a significant difference in spindle normality in oocytes in the pregnant patients compared with oocytes in the non-pregnant patients (100% versus 33%, P < 0.001). Spindle density was significantly higher in those oocytes resulting in pregnancy (3.0 +/- 1.23 nm versus 2.5 +/- 0.7 nm, P = 0.02). These oocyte markers may provide a useful non-invasive tool in the selection of the embryo most likely to produce a pregnancy.