For (time-saving) practical considerations, the following additional selections methods were used: word of mouth advertising, distribution of letters in districts with many children, and recruitment through representative panels of selection agencies in the above-mentioned cities. Only pregnant women treated by a midwife were included. In The Netherlands, women with serious complications are treated by a gynaecologist rather than by a midwife or an obstetrician. (The concept of obstetrician does not exist in the Dutch health system.) Such women were thus excluded
from participation.