RZL I am so sorry for your loss.... my condolences to you and your wife, I can't imagine what you must be going through
NICE guidelines (Sept 2007) state that intermittent auscultation of the fetal heart should occur after a contraction for at least 1 minute, at least every 5 minutes.
But I'm sure that normal practice is for the heart rate to be monitored after EVERY contraction during 2nd stage. See point 2.7 according to the World Health Organisation's publication Care in Normal Birth
If the mw was finding it difficult to pick up the heart rate she should have called for back up, but (being Devil's advocate) perhaps she daren't leave your wife to go get it! Mw do work in appalling conditions within the NHS, with staff shortages, overwork etc... Not any consolation to you and your wife but it may be that your case can add to the argument over NHS funding by the government (in general) and be a wake up call to your local hospital's policies in particular. I bet that mw is devastated too, whether or not it is proven she was negligent.
The sad fact is that birth is a risky business and some babies do die or suffer injury. It is very rare these days, because we do have better hygeine and good nutrition, and most often an exact reason is hard to find. Which does not help you at all.... I know of someone else who recently lost a baby at birth even though she underwent a Crash CS under general anaesthetic. Brain injury is thought to have occured shortly before birth. This poor lady is also looking for answers.
Be good to your wife (and yourself!), accept all offers of support from friends and family and don't be afraid to talk about this, it will help the grieving process.
My thoughts are with you both.