As technical advances become more complex, care has come to be increasingly controlled by, if not carried out by, specialist obstetricians. The benefits of this trend can be seriously challenged. It is inherently unwise, and perhaps unsafe, for women with normal pregnancies to be cared for by obstetric specialists, even if the required personnel were available. Specialists caring for women with both normal and abnormal pregnancies, because of time constraints, have to make an impossible choice: to neglect the normal pregnancies in order to concentrate their care on those with pathology, or to spend most of their time supervising biologically normal processes, in which case they would rapidly loose their specialist expertise.
Midwives and general practitioners, on the other hand, are primarily oriented to the care of women with normal pregnancies, and are likely to have more detailed knowledge of the particular circumstances of individual women. The care that they can give to the majority of women whose pregnancies are not affected by any major illness or serious complication will often be more responsive their needs than that given by specialist obstetricians.
-A Guide to Effective Care in Pregnancy and Childbirth,
Enkin, Keirse, and Chambers, Oxford University Press