Laser zona pellucida thinning - an alternative approach to assisted hatching

BACKGROUND: The purpose of this study was to assess the efficacy and hatchi ng characteristics of in-vitro cultured human embryos subjected to laser zo na pellucida thinning. METHOD: Zona thinning was performed on 110 embryos u sing a non-contact 1.48 mum diode laser and the hatch rate in vitro was com pared with 42 control embryos. Variation of zona thickness and degree of zo na expansion was assessed. Scanning electron microscopy was performed on em bryos entrapped during hatching to identify the site of hatching. RESULTS: The rate of hatching was significantly higher in laser thinned blastocysts compared with control embryos (68 versus 33% respectively, P<0.01). Laser t hinning increased the variation of zona thickness in embryos from 11.6-27.3 %. Natural zona thinning occurred in 92% of laser thinned hatching blastocy sts and 100% of control embryos. CONCLUSION: These results suggest that las er zona thinning is effective and may provide significant advantages over c onventional assisted hatching techniques, which create holes.