1. Background: Most research in obstetrics is based on outcome criteria. International studies describe that intervention-rates in midwife-led units are at par or lower than at conventional consultant-led units with a positive fetal and maternal outcome. Research for decision-guidelines which might influence these differences is rare.

2. Aim and Objectives: Aim of the study was to explore the decision-criteria applied by obstetricians when carring out obstetrical interventions (focussed on the interventions caesarean section, episiotomy, induction of labour and cardiotocography).

3. Method: Longitudinal qualitative study. Problem-centered Interviews (T1: n=26; T2: n=23) were conducted according to Witzel at a hospital with a MDU and a control hospital with a consultant-led unit. Interviewed staffs were obstetricians, executive’s midwives and administrative directors.

4. Results: 20 categories which contribute to the decision for or against interventions were identified. Results show a dominance of medical indications in the decision process as well as a strong inclination towards intra-departmental guidelines. Professional experience, maternal request and hierarchical structures also affect the decision-making process. Intuition, exchange with midwifes and colleagues, competition of other hospitals, attitudes of physicians in private practise, forensic validation and medical progress were described. Also structural conditions and subjective components were noticed for the decision-making procedure. Vocational education did not play a crucial role but publications showed an influence. The implementation of midwifeled care had no effect on decision-making criteria and the criteria did not change over time. In general the implementation of midwife-led care got a positive appraisal.

5. Conclusion / Implication: Results show a multitude of decision-making criteria which were systematically investigated. There are no short-term consequences on obstetricians’ acting after the implementation of midwife-led care. This fact and the positive appraisal can contribute to increase obstetricians’ acceptance of midwife-led care.