what are the reasons for i.v.f. failur?

Answer 1

There are many reasons for I.V.F. failure and the reason for failure can occur during any step of the process. So it would be easier to link you to a site that explains each step and what during that step can lead to a failure.

http://www.ivf.com/overview.html

But, in a nutshell, reasons for failure are canceled cycles, failure to collect eggs, failure of fertilization, and failure of implantation (could be due to defective embryo or endometrium, or poor synchronization).