Factors associated with fractured zonae pellucidae in an in-vitro fertilization programme

Oocytes with fractured zonae pellucidae (FZP) were recoveredin 43% of cycles in our programme of in-vitro fertilization(IVF) and embryo transfer. Amongst all the recovered oocytesthere were 16% FZP oocytes, in which fertilization was precluded.The mean number of punctured follicles and the success rateof oocyte recovery were significantly higher in cycles yieldingoocytes with fractured zonae compared with cycles yielding onlyoocytes with intact zona pellucida oocytes. A damaged zona wasfound only in healthy mature oocytes and its occurrence wasrelated to the size of the syringe used for follicular aspiration(6.6 versus 20.1% with 10- or 20-ml syringes, respectively,P < 0.001), and not to the form of ovarian stimulation orfollicular characteristics. The proportion of cleaved embryosafter the insemination of oocytes with intact zonae was lowerin patients also yielding oocytes with fractured zonae (74 versus86%, P < 0.001); however, the pregnancy rates after embryoreplacement were the same in both groups. We conclude that thetechnique used for follicle puncture may damage the integrityof zonae pellucidae of healthy mature oocytes. This phenomenonwas estimated to be responsible for {small tilde}15% of failures(16 versus 19 pregnancies per 100 cycles) in our IVF programme.