Hi Astrid,
I have just finished my midwifery diploma in which I had 15 follow through women so this is what I did. My role (which is in the hospital I work in, just incase each hospital is different) had two different components. If I was rostered on to work I was the midwife who supported the woman under the supervision of a registered midwife like I would everyday at work. This involved all cares/support for the woman, baby and being the midwife for the birth. If I was there when I wasn't rostered on I was only there in the capacity of a support person only and was there solely for the woman and being her support/voice/advocate. I wasn't involved in any of the midwifery care or birth.
I hope you don't mind but I would just like to say speaking from both sides, a student and having a student midwife in my birth. Being a student it was an amazing experience that a woman allowed me to be present and involved in her pregnancy and her birth experience. Being involved in her antenatal care I was able to build a relationship and it was so rewarding to be there during her birth.
On the other side of the experience and being a follow through case study myself having a student midwife in my labour was also fantastic as she was an additional support and gave me so much encouragement and empowerment she helped me through and also my DH. Once again I was able to have a relationship with her through antenatal and work.
Will the trainee midwife be following you through antenatally and postnatally as well as your birth?
Hope that helps and I haven't confused you (Hope you don't mind me adding my 10cents, can't help myself sometimes, LOL!).