At which point after conception does life begin? According to Buddhist teachings (of any school) at what point does a human life begin? Is it at conception, during a particular point during pregnancy, at birth or even after birth? Does it differ between schools and Buddhist cultures?

I suspect the nidanas might be instructive on this point but I'm interested in answers that may or may not include them.
Patisandhi Citta is the starting point of life. So life begins at conception. 

Rebirth Consciousness


  This is called pa.tisandhi citta, literally "relinking consciousness."
  The pa.tisandhi citta is the act of consciousness which arises at the
  first moment of life, the moment of conception. It is determined by
  the last kammic citta of the preceding life.
  
  This kammic factor for the arising of a being operates through the
  pa.tisandhi. The accumulated tendencies of past lives are carried on
  to the pa.tisandhi and so the process of being born, dying and being
  born again goes on. Each pa.tisandhi citta is a new one, not the
  continuation of the old one in the previous life. Thus there is no
  place for a soul concept in rebirth. In the course of one particular
  life there is only one pa.tisandhi citta. Once the function of linking
  two existences has been performed by the pa.tisandhi, consciousness in
  the newly formed embryo immediately goes into the bhava"nga state.
  This flows along in the new existence with infinite interruptions by
  various stimuli and ends as the cuti citta of that particular
  existence.