Hi there, don't know if this is still relevant but I'm also a midwife and took off 5 weeks in all.  I returned to work on 7.5hr shifts and only worked on p/n ward for a few weeks until I had more energy and felt fully healed (which I had been told was 12 weeks).  There is no way I could have managed 12hr shifts on L/W, I was exhausted after the shorter shifts!  Good luck